THE JOURNAL

QUEKETT MICROSCOPICAL CLUB.

VOL. Ill

1872—1874.

I WOODS ;

\ HOLE^ MASS,

[Published for the Club,]

ROBERT HARDWICKE/ 192, PICCADILLY

G. P. BACON, ITvINTEE, LEWES.

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I WOODS \ HOLE, THE JOURNAL X^'ASS.

^aelictt ||licrost0}j'ual €\nh

Observations on the Polyzoa. By a. H. H. Lattey, M.R.C.P.*

(Bead October 27th, 1871.)

Amongst the vast number of animated beings, of whose very- existence we should have remained in profound ignorance, were it not for the invention of the microscope — so justly termed a sixth sense — few afford more beautiful or interesting objects for our con- templation than the group to which the name of Polyzoa has been given ; so called from two Greek words — polus (many) and zoon (animal) — being always found aggregated together in masses, and many of them resembling minute plants, so much so as to have l)een classed, by early observers, amongst the members of the vegetable kingdom. Their complex organization has obtained for them a high position in the animal kingdom, and the exquisite form which some of them possess cannot fail to excite our admiration. When, for instance, we see the elegant Sertularians, projecting like fairy ferns from the side of a rock-pool, attractive by their graceful forms, even before the microscope has revealed the beautiful little creatures studding their branches like living flowers, or the Poly- zoary of the Halodactylus, with its exquisite bell-shaped creatures emerging, one by one, from the jelly-like mass coating the seaweed, like the ribs of a folded umbrella, stripped of its covering, and then gradually expanding into a beautiful bell, the cilia? fringing its ribs, or tentacles, in perpetual motion, keeping up a constant eddy in the surrounding water, so as to bring the floating particles of nutritious matter within the grasp of their open mouths.

* Communicated by Mr. T. Curteis, F.R.M.S. JouRN. Q. M. C. No. 18. B

Z A. H. H, LATTEY, OBSERVATIONS ON THE POLYZOA,

Amongst all these creatures, none are more curious than the species of Bugula, called Bugula Avicularia, from its possessing those strange appendages called birds' head processes, and most appro- priately so, from their very exact resemblance to the head and beak of a bird. They are attached to the margins of the cells by means of a footstalk, and each has two " mandibles ;" the upper one fixed and the lower one moveable, just as in birds, and they are opened and shut by powerful muscles wdthin the " head." A most singu- lar and curious sight it is to watch the movements of these "ob- jects" when a portion of the Polyzoary is viewed under an inch or two inch objective, so as to allow a number of these bodies to be in sight at once. It will then be seen that each head keeps up a con- tinual nodding movement, throwing itself slowly back, which its joint-like union to the cell allows, at the same time gradually open- ing its jaws, or rather depressing the lower jaw until the mouth is opened to its full extent, and when the head has gone back as far as it can reach, it suddenly resumes its former position, the mouth closing at the same instant with a sudden snap, and entrapping any luckless animal that may be passing at the time, and then the same proceeding takes place over and over again, without any in- termission. It certainly is a most singular — I might almost say ludicrous — sight to see all the avicularia within the field of the micro- scope practising this perpetual " snapping." The great size and apj)arent strength of the animals which they are capable of seizing and retaining in their grasp, must impress us with a sense of the enormous strength of the muscles which move the jaw, for they seize and retain not only small vermicules, but such large creatures as caprellee, entomostracse, &c. ; and very curious it is to watch the wiithings and struggles of one of these comparatively gigantic vic- tims in its vain efforts to escape from the jaws of its tiny captor. Not unfrequently the captive is seized by another, or even two more avicularise, in other parts of its body, thus making assurance doubly sure, and so deadly is the grip, that I have never seen one of them relax its hold on the application of the medium which is fatal to themselves.

Various have been the conjectures as to the office of these " heads without bodies," and their exact function in the economy of the ani- mal— some supposing that their office is to protect the delicate creatures over whom they mount guard from the rude contact of foreign bodies which might injure their frail structure ; but many

A. H. H. LATTEY, OBSERVATIONS ON THE POLYZOA. O

equally delicate animals, the Halodactylus for instance, are unpro- vided with any such protection. Others suppose that they are destined to entrap the passing animals, and hold them in their firm grip until decomposition has diffused them in the surrounding water, thus furnishing the creatures with a supply of nourishment ; this, to my mind, appears the most feasible explanation. I have found these animals in great abundance at Ilfracombe, especially upon the rocks near the harbour, mostly depending from their under sur- face ; the Campanularia Dichotoma in the same locality on the leaves of brown sea-weeds, and the Sertulari^ growing from the sides of rock pools at St, Leonards and Exmouth. The Halodactylus may be found in any locality where there are rocks, encrusting the stems and fronds of the common bladder wrack (fucus vesiculosus) at low water, especially during spring tides. It looks like a firm gela- tinous coating of a brown colour, and has a semi-transparent appearance. When put into fresh sea water, it is seen to be- come gradually, as the animals emerge from their cells, overspread with what appears, to the naked eye, to be a minute white downy covering.

If it is desired to make preparations of any of these creatures, the following will be found a successful plan. Their extreme sensi- tiveness, and the rapidity with which they withdraw themselves into their cells upon the slightest touch or jar, makes it necessary to adopt a peculiar plan of proceeding. I would premise that before commencing operations with the Halodactylus it is desirable to cut it into the length required to fit the cell in which it is to be placed whilst the animal is contracted, as it may then be cut in any direction without injury, but when expanded it requires to be very carefully handled, as if the bells are in any way pressed or put out of shape they cannot be restored. For this reason it should be so cut as to fit the cell tightly so as to prevent its being shifted. The object is to coax the animals out of their tiny homes, and to keep them out until you can kill them. To accomplish the first object, it is best to keep them out of the water for several hours, and then to put them into fresh sea-water in any appropriate vessel. I have found a circular glass dish, such as is used for cakes of trans- parent soap, answer very well, as it can be put upon the stage of the microscope, and the effects of different stages of the operations watched, which is of importance. Some alcoholic spirit mii«t now be added very gradually — spirit of wine, brandy, whisky, or gin.

4: A. H. H. LATTEY, OBSERVATIONS ON THE POLYZOA.

it matters not which — when they will be observed to come out in greater numbers, evidently attracted by the taste of the spirit, and as it continues to be added they become evidently excited, with- drawing into their cells, and coming out again, bending about, and the ciliee meanwhile moving in the most rapid manner. This con- tinues for some time, until at length they begin to flag in their movements, which become more and more sluggish, the animals being apparently drunk. This is the moment to pour off the alcoholized sea-water, and pour upon them the preservative fluid, which has the desired effect of bringing out all that are still left in their cells, and gradually killing them, and it has the immense advantage of being at the same time a most excellent fluid for pre- serving them, so that they can remain in it. I find it of great ser- vice to let the Halodactylus lie for a considerable time in this fluid before finally putting them up, as a certain amount of deposit takes place from the sea-weed, which it is better to exclude from the cell. The preserving fluid I use is one recommended by Dr. Beale, as a modification of Thwaites', and is prepared as follows : —

Mix three drachms of creosote with six ounces of wood-naphtha, and add, in a mortar, as much prepared chalk as may be necessary to form a smooth thick paste ; water must be gradually added to the extent of 64 ounces, a few lumps of camphor thrown in, and the mixture allowed to stand for two or three weeks in a lightly covered vessel, with occasional stirring ; after which it should be filtered and preserved in well-stopped bottles.

[Notice.— Plates i. and ii., illustrating Mr. Furlonge's paper on the Flea, will be issued with the next No. of this Journal.]

On the so-called " Nerve" of the Tooth. By T. C. White, Hon. Sec. {Read October 27^/^,1871.)

There is no field of microscopical investigation more pregnant with, interest than that which comprises the study of the histological characters of the various elements that help to make up the sum of the animal frame. I would not in saying this seem to depreciate those other subjects in which lovers of microscopy find such delight. Micro-zoology, the physiology and structural elements of the vegetable world, and those studies having for their object the development and correction of the higher powers of our micro- scopes, possess their several interests, and are very important as fields of research ; but I believe they will be found to pale before that study which enables us to arrive at a knowledge of those structures which build up and bind together the various organs of the human frame. A vast amount of work has yet to be done in comparing these several tissues with those of the lower animals, both as regards their embryonic condition as well as that of adult life : but it is not of comparative histology, nor of histology in its general aspect, that I would speak to-night, so much as of one particular tissue for which all present have, doubtless, at one time or another, felt a peculiar interest — I mean what is called the " nerve'''' of a tooth. Great uncertainty exists in the popular mind relative to its exact locality and nature ; all know it to be a very painful subject, not to be touched upon except very lightly, and many desire to see what it is like. Now it occurred to me that it might not be altogether an uninteresting subject to bring- under your notice, and while we were enabled to see what structural elements even so small a portion as this might afford for our powers of observation, it might at the same time stimulate the members of oar Club generally to work out systematically the histology of the other structures of the animal frame. These fields have been well worked by others, it is true, but we reap the harvest of their labours in the many manuals on the subject with which our scientific libraries abound ; but though skilful gleaners in the field of scientific investigation leave little for us to gather, yet stray facts may still

O T. C. WHITE OX THE SO-CALLED " NERVE OF THE TOOTH.

be picked up by diligent and careful, but above all sf/ste/natic observers.

I trust that you will deal leniently with me if I presume for a moment that you know nothing whatever of the various structures entering into the formation of a tooth. I can thus, in an elemen- tary manner, recall to your minds the osseous elements we meet with in our examination. If a tooth be divided longitudinally the main body of such a section would reveal three different substances surrounding a cavity, which, to a certain extent, partakes of the external shape of the tooth ; immediately surrounding the cavity, and constituting the principal bulk of the tooth, we notice a fibrous silky substance, called the " dentine ;" capping that part of the dentine which appears above the gum, we see the crystalline, almost msensible '^ enamel,^^ designed to protect the highly organised and exceedingly sensitive dentine beneath it ; we shall also observe that the dentine inserted in the jaw, and forming the root of the tooth, is clothed with a material of a different appearance to the other two substances — that is called the " cementumJ^ Of the enamel and cementum, it is not necessary on this occasion to speak, but the im- portant relation existing between the '' nerve " and the dentine demands that I should enter more into detail in explaining its microscopical appearance. In looking at a section of dentine under the microscope in a well-developed human tooth, one is reminded of those views of the comparative sizes of the rivers of the world given in some atlases, only here our rivers are all the same diameter and about the same length, and run together in parallel waves. If, for the sake of illustration, we speak of them as rivers, we should say that they arise beneath the enamel by exceedingly fine tribu- taries, by the confluence of which the main stream is gradually enlarged till, flowing on towards the centre of the tooth, its '^ de- bouchure " helps to make up the walls of the central cavity, which is occupied in the living state by the so-called " nerve." A closer examination of our metaphorical rivers with higher magnifying powers will show us that they are tapering and undulating tubes, and existing so abundantly in the dentine as to impart to it that fibrous silky aspect which cannot fail to strike the most casual observer. These tubes, which, on the walls of the cavity, measure about x-o-^Tjiyth of an inch in diameter, are occupied in a recent tooth by transparent structureless fibres known as the dentinal fibrillge, the exact office of which is but obscurely defined, but they may

T. C. WHITE ON THE SO-CALLED "NERVE OF THE TOOTH. 7

minister to the nutrition and vitality of the tooth, since, when from age or disease these tubes become consolidated, the fibrous structure is re^Dlaced by one resembling horn, and, as a consequence, the tooth dies, becomes loose and a source of painful irritation. If a section of the dentine be made in a direction that shall cut across the course of these tubes, each tube will present an irregular aper- ture, and will be seen separated from its fellows by an almost equal proportion of intertubular tissue. We need not now consider any further the character of the dentine, as 1 shall have to recur to it when speaking of its relation to tlie nerve ; but what I have laid before you will enable you to understand the meaning of much of the structure it is our especial object to examine in the central or pulp cavity of a tooth.

If we take a recently extracted healthy tooth and split it we shall notice that the pulp cavity is occupied by a pinkish fleshy mass about j of an incli long and -jV^li of an inch wide at its upper and thickest part ; it partakes somewhat of the external shape of the tooth, being wide in the upper part, and tapering towards the tooth : this, then, is what is popularly called the " nerve." In physiological parlance it is termed the pulp. The basis of this pulp is composed of areolar tissue, whose interstices are filled with a homogeneous plasma. *

A microscopical examination of its exterior will reveal an infinite number of small points, giving to it an appearance not much unlike the cross section of the tubes of the dentine, both as regards size and distribution. Having noticed this much, recourse must be had to compression before we can readily make out the arrangements of its internal structure. Before proceeding to flatten it by pressure it may be withdrawn from its cavity, and allowed to soak in the ammoniacal solution of carmine, recommended by our President in his book " How to Work with the Microscope ;" let it remain in it twenty-four hours, wash away the carmine fluid, and transfer it to glycerine for a few hours ; then put it under gentle, gradual pressure for some few hours more, when it will be rendered sufiiciently thin to be easily examined by a \ oi an inch objective or higher powers.

Commencing our examination at that part of the pulp nearest the apex of the root, we shall notice it entering the foramen of the fang as a fine thread, which though so fine nevertheless con- veys the nerve and the artery into the pulp, and gives exit to the

8 T. C. WHITE ON THE SO-CALLED '^ NERVE" OF THE TOOTH.

returning vein ; tracing this thread into the pnlp we shall readily distinguish the nerve as a bundle of parallel fibres which, running in together a short distance, divide into two, three, or four fasciculi, and dividing again still give off fibres to every part of the pulp ; it is highly probable that these fibres end in loops, but the pressure necessary to reduce the pulp sufficiently thin for observation rup- tures the loops, and consequently they very frequently appear to terminate in free extremities ; but one fact may be easily demon- strated, namely, their course is always at right angles with the dentinal tubuli. Besides the ramifications of the dental nerve the pulp also contains the branches of the artery and its vein; these are not so easily followed, but in an examination of the pulp of a tooth extracted for severe inflammation in it, the congested vessels were naturally injected, and could be seen as a complicated net- work without any definite arrangement excepting a loop -like dis- tribution towards the circumference ; in some cases the vessels of the pulp, becoming stained by the carmine, will be readily seen with their peculiar transverse nuclei and distinguishable from the areolar tissue, whose nuclei are spindle-shaped. There is one feature in the microscopical examination of this prepared pulp which will not escape observation — it is the curious arrangement of its cortical portion. In referring to the microscopical appearance of the ex- terior of the pulp, as it appears on first splitting a tooth, I alluded to the comparative likeness presented by it to that of the dentine cut across the tubes, and if that comparison is borne in mind in the examination of this external portion of the pulp, under its present circumstances, we may easily interpret the meaning of this arrange- ment. The cortical substance of the pulp in its healthy condition con- sists of a number of oval bodies placed side by side with their long axes perpendicular to the surface of the puljD on which they stand ; they are deeply stained by the carmine, which proves that they are endowed with active and growing powers. These oval bodies are termed '' Odontohlasts.''^ An examination of an odontoblast, which has been isolated by pressure from the others, will show that it has an attachment by a transparent structureless appendage to some- thing within the body of the pulp, while a similar appendage, pro- ceeding from its distal extremity, penetrates a tubule in the dentine, and becomes the dentinal fibril of Tomes.

The odontoblastic layer of the pulp is so important an element in the life and histology of a tooth that its history deserves a closer

T. C. WHITE ON THE SO-CALLED " NERVe" OF THE TOOTH. 9

examination than tlie limits of a paper like this can afford ; but it may be interesting to show the part it plays in the formation of the dentine.

About the sixth or seventh week of embryonic life a groove is formed in either jaw^, at the bottom of which, after the lapse of a few weeks, papillae begin to arise, and shortly after transverse par- titions in this groove shut off and separate each papilla, which then becomes the representative of the future temporary tooth. About the seventh month of foetal life the ossification of the tooth com- mences, and the dentine is represented by a cup-shaped scale cap- ping the crown, and ultimately extending down the sides and em- bracing the whole of the upper surface of the pulp. Jt is at this period of their growth that the odontoblasts are most active, for they have the development of the dentine before them, and deriving a plentiful supply of nutrition from the plexus of bloodvessels beneath them, dentine is formed through their agency from without inwards, till the pulp being reduced to the size at which we gene- rally see it by the gradual formation of the dentine, the odonto- blasts become dormant, but capable of awaking to activity under the influence of certain circumstances of irritation ; thus if caries attacks a tooth at a particular spot the tubuli in the dentine, through the fibrillae in them, become consolidated at an equal dis- tance from the j)oint of attack all round it, and a barrier seems to be thus thrown up against the inroads of the advancing enemy ; but unless such a remedial measure as the careful excava- tion of the carious portion of the tooth and subsequent plugging of the cavity be adopted, barrier after barrier may be thrown up but to be overcome. Even then the odontoblasts of the pulp resist by forming new dentine in its very substance, and it is only when in- flammation and suppuration destroy the odontoblasts that this re- parative process is annihilated. In some cases of general irritation of the pulp, as where the crown of a tooth is worn through by the grinding down and wear of mastication, the whole of the pulp may be converted into an irregular dentine. Sometimes nodules of ossific matter are found in the meshes of the areolar tissue of the pulp, but these do not partake of the character of the dentine, but are semi-transparent and structureless, testifying to the amount of bone-producing matter in the homogenous plasma saturating the body of the pulp, but which it is the legitimate office of the odon- toblasts to build up as dentine.

10 T. C. WHITE ON THE SO-CALLED " NERVE" OF THE TOOTH.

There are great and, I fear, almost insuperable difficulties in tlie way of clearly seeing the termination of the nerve fibres in the pulj) ; one can only conjecture at the method in which they end. In some specimens two fibres may be seen running side by side for some distance, and when you expect to see a loop the ends are found separated ; this may probably arise by the pressure used to render the pulp thin enough for observation. Some specimens, again, show a very apparent looping of the fibres, but the loops extend round the circumference towards the end of the pulp, they are so large ; but in no case have I met with fibres that would lead us to suppose that were they small enough to enter the tubuli that they do so. How, then, are we to account for the painful sen- sation experienced in cutting into live dentine, unless we suppose that a connection of some kind exists between the tubuli and the fibres of the nerve ? The only theory that can be suggested is that the dentinal fibre contained in a tube of the dentine passes out through its odontoblast, and then, becoming fused with the nerve, conveys the sensation to the brain, and we are conscious of the irritation.

I have not found it possible to see this connection between the odontoblast and the nerve fibres, because the re-agents usually em- ployed to render nerves visible, dissolve away the odontoblasts ; neither have I, by means of thin sections, been more fortunate, as the proximal caudal appendage of the odonto blast is too trans- parent and too minute to admit of demonstration, except, per- haps, by the employment of new re-agents ; in specimens of the pulp, that after staining with carmine have been teased out with needles, the isolated fibres have had, besides their own coloured nuclei, coloured odontoblasts, with this internal caudal appendage fused into their outer parts. Such may be the general mode of their connection, but I am not clear on that point. Such, then, are a few of the principal elements met with in a microscopical examin- ation of what is popularly termed the '■^nerve''' of a tooth, but incase any member present may feel inclined to work out these details for himself, it may be as well to append a few remarks relative to the plans of investigation, attended by the best results. The teeth employed have been temporary teeth, removed in a healthy con- dition, to make room for the advancing permanent set, any others being unsuitable from disease. It is necessary to exercise great care in extracting the pulp from them, as the bone dust from the

T. C. WHITE ON THE SO-CALLED " NERVE" OF THE TOOTH. 11

tooth and impurities of various kinds cling most tenaciously to tlie odontoblasts, and not only obscure the view of the delicate details, but look unpleasant and slovenly. The plan found to answer best is to file a longitudinal groove round the tooth ; then, having washed away all the debris very thoroughly, split the tooth with a pair of wire nippers, when it will come clearly in two and expose the pulp for its whole length, when it may be withdrawn by seizing it at its smallest part and tearing it out of the cavity. This will draw out not only the odontoblasts but some of the dentinal fibres attached to them. Another very good plan for observing the relation of the pulp to the dentine is to soak the tooth for a few weeks in the carmine staining fluid, which becomes sucked up through the foramen of the fang, and being absorbed by the pulp, colours it completely. The tooth may then be decalcified by immersion in ordinary hydrochloric acid, which removes the lime but does not hurt the soft tissues. At the end of a fortnight the tooth may be cut in thin slices, when the pulp will be cut with the decalcified osseous tissue, and the relation will be well shown. I have thus, in these few brief remarks, which fail to do justice to my subject, endeavoured to show you that that which is generally called the nerve of a tooth is in reality a mass of areolar or connective tissue, through which ramify the nerve, vein, and artery destined for the life of a tooth, that its function originally was the formation and building up of the dentine, that its powers in adult life remain dormant, but capable of being aroused under the action of a stimulating influence to develope dentine again, and that it performs an important part in ministering to the vitality of a tooth, as well as constituting a tooth a very delicate sensory organ. These few remarks, there- fore, will, I hope, have the effect of inducing others to take up the comparative histology of the pulp, and lead them to investigate its tissues in some of the lower animals, both in their foetal condition and at maturity, and I can promise them a rich reward in return for their labours in new fields of observation open, and fresh revela- tions of the skill of the Great Architect of All.

12

On the Internal Structure of the Pulex Irritans, By W. H. Furlonge.

{Read Fehruary 2Srd, 1872.)

Before entering upon the subject of the second portion of my communication on the Pulex irritans, viz., its internal structure, I think it desirable to state, that I have not been able to resort to actual dissection of the insect, in aid of my observations. In fact, it appears to me, that such extraordinary manipulatory skill would be required to dissect so minute a creature, that any attempt to accomplish such a task, would prove almost abortive, even to the most practised eyes and fingers. Fortunately, how- ever, such is the transparency of the chitinous envelope of the insect, that it is possible to observe every organ, almost as perfectly as if enclosed in glass, even when employing such com- paratively high powers, as the ^in. Nevertheless, I have been obliged to leave wholly untouched some portions of the internal structure of the animal, such, for example, as the nervous system, and several of the glandular organs, and I shall be greatly pleased if other workers, of greater anatomical skill, will shortly fill up the gaps I have left in this investigation.

The internal structure of the flea may be conveniently described under the following heads : the alimentary and digestive system with the organs pertaining thereto, the respii-atory system, and the reproductive organs.

1st. — The Alimentary and Digestive System.

In my previous paper I have stated that I regard the commence- ment of the alimentary canal as a slender fleshy proboscis, perforated by a canal, through which the blood is sucked directly, and very rapidly, into the first stomach by the constant powerful muscular action by which the insect is enabled to dilate its external en- velope. In the course of my investigations I have had occasion to preserve individual insects alive for weeks together, and, there- fore, to feed them, and thus I have had very numerous opportunities of observing the process of imbibition. My method of procedure was to keep the insects in a corked test tube, and when it was desired to feed them, I inverted the tube upon my wrist or forearm. The creatures almost instantly fastened on the flesh, and usually

. W. H. FURLONGE ON THE PULEX IRRTTANS. 13

stood on their heads, as it were, plunging their mandibles deeply into the epidermis, at the same time rapidly and powerfully dilating their bodies by alternately shortening and elongating them ; and I may observe that I have never been able when feeding my captives to detect the slightest prick or wound from the insertion of their mandibles. In the course of two or three minutes, the first stomach becomes gorged with blood, and if the insect is permitted to remain undisturbed, the blood passes on to the second stomach, presently to be described, the animal emitting jets of dark and semi-digested blood from the anal orifice with such force as sometimes to project the contents of the second stomach to a distance of one or two inches.

In examining the position and structure of the alimentary and digestive organs, I have found it desirable to select a young and transparent male specimen, as from the absence of the ovaries, and the partially matured eggs which are generally to be found in the female, the course of the digestive canal is more clearly seen. A suitable specimen being found, it is to be kept for about two days without food, then fed in the manner I have described, but not per- mitted to remain on the skin for more than a minute, when it is to be removed and stupefied by the insertion within the test tube of a morsel of blotting paper containing a very small quantity of chloro- form, when it may be placed in the compressor, and gently flattened between the glasses by a very gradual tightening of the screw:

When viewed under such circumstances in a good binocular with a y^^ths objective, by transmitted light, and especially by dark ground illumination, the sight is extremely interesting, and, I think, very beautiful. The first stomach filled with the bright crimson freshly ingested blood is seen to be undulating incessantly in the manner I attempted to depict by the dotted lines in the drawing of the Pulex exhibited in the reading of my last paper, and since engraved in our Journal. This energetic peristaltic movement — amounting in fact to a violent churning action — 'Of the stomach, sometimes proceeds from the anterior extremity, undulating back- wards, and sometimes the wave originates and proceeds in the reverse direction, as many as two or three waves being often seen in progression at the same time. By this churning action the blood is regurgitated violently backwards and forwards in the stomach, and is, as I think, in this way brought into contact with the gizzard, a very interesting organ presently to be described.

14 W. H. FURLONGE ON THE TULEX IRRITANS.

The first stomacli of tlie flea possesses a very remarkable struc- ture. It is, in proportion to its size, of extraordinary thickness and muscularity ; in fact, it is so banded and cross-banded by thick muscular fibres running in all directions, that it presents the ap- pearance of a reticulated structure; indeed, under the ^in. objective, "when filled with blood it resembles nothing so much as a closely but irregularly knitted purse of thick crimson silk. It is, no doubt, by the powerful contraction of these muscular bands, that the violent movements I have described are nAintained. PI. i., Fig. 1 shows the appearance of the structure of the stomach as magnified 200 dia- meters.

The Gizzard. — Situated at the anterior orifice of the stomach, immediately behind the entrance of the canal, which conveys the blood from the suctorial proboscis, may be observed a dense semi- opaque muscular organ, in shape similar to an ogival-headed shell, the conical end being projected forwards, and receiving the ex- tremity of the suctorial canal, the orifice of the stomach surround- ing its base. By careful illumination wdth a strong light, the structure of the gizzard may be made out to consist of a dense and very thick substance, surrounded by a reticulation of muscular fibres, somewhat similar to those of the stomach, but the meshes, so to speak, being more close and regular. In the living insect this organ is generally to be seen in constant movement (if the specimen is not too much compressed) elongating to about twice its normal length, and then suddenly contracting, and at first sight might be taken for a heart, or blood-circulating organ, so constant and regular are its pulsations in some cases. In reality, however, it is a gizzard, by means of which the blood corpuscules are ground up or disin- tegrated until fitted for digestion in the second stomach.

I have in this place the pleasure of mentioning a somewhat curious circumstance of peculiar interest to the Club, as it relates to the distinguished man from whom we derive our name — the late Professor Quekett. I am indebted to Mr. Parkes, of Birmingham, who enjoyed the privilege of his intimate acquaintance, for the fol- lowing anecdote : — In a discussion upon the structure and functions of the digestive organs of insects, it was observed in the presence of Mr. Quekett, that suctorial insects are not furnished with any gizzard or grinding apparatus, such organs being, in fact, unneces- sary for the assimilation of their food. While assenting to the general proposition, however, Mr. Quekett, with the sagacity he

W. H. FURLONGE ON THE PULEX IRRITANS. 15

possessed in so remarkable a degree, maintained that in the case of the flea a gizzard ovglit to be found, as, in his opinion, some such apparatus would be requisite for the purpose of breaking down the blood discs and preparing them for assimilation. It was not until some time after the death of Mr. Quekett that the actual exist- ence of the organ he had predicated was demonstrated, the flea's gizzard having been dissected out and isolated for the first time, I believe, by Bourgoyne, of Paris. We must regret that the Pro- fessor did not live to see the truth of his conjecture thus con- firmed.

More skilful fingers than my own have enabled me to figure the accompanying drawing (Fig. 2), which has been taken from a pre- paration by Mr. Topping. With admirable skill this minute portion of the insect's structure has been isolated, and laid out upon the glass slide. It will be seen to possess the well-defined and powerful muscular structure common to the gizzards of insects, though the teeth or rasping appendages usually found in such insects as feed upon hard food are wanting. In the flea's gizzard, however, such aids would have been clearly unnecessary, the breaking down of the blood corpuscules being, as is easily conceived, rapidly and perfectly accomplished by the passage of the food between the rubbing sur- faces of the organ when actuated by its powerful muscular bands.

The Second Stomach, or Intestinal Sac. — The blood constituting the animal's food having been thus triturated, passes on through a comparatively short and straight gut or intestinal canal, which is furnished at its junction with the posterior extremity of the stomach with a powerful sphincter muscular valve, controlling the passage of the food, into the digestive sac or second stomach, as it may be termed. In most specimens of the insect that I have examined, the capacity of this sac seems to be almost, if not quite, as large as that of the first stomach. The second stomach, like the first, is sub- jected to constant dilations and contractions, but these do not occur in waves or undulations ; in fact, the sac being sub-globular inform, and not elongated, like the first stomach, its contractions 'are necessarily accomplished in a different manner. Moreover, the walls of the sac are not themselves muscular, and therefore its movements are not produced by the contractions and dilations of the parietes themselves, but by the agency of muscular bands attached to them, which are set in action at different times, and seem to pull the walls of the sac together, from side to side, by which movements the fluid

16 W. H. FURLONGE ON THE PULEX IRRITANS.

contents of the sac are kept in a state of constant motion, tliougli much less violently than those of the first stomach.

The Rectal Papillce. — Within the intestinal sac are suspended six curious conical teat-like organs, shown in Fig. 3. These organs will be at once recognised by those who are familiar with Mr. Lowne's work on the " Blow-fly," as the rectal papillas, or urinary organs of the insect. I must, indeed, candidly say, that but for Mr. Lowne's observations, it is very possible that the existence of these organs in the flea would have escaped my notice, as, owing to the generally dark colour of the semi-digested contents of the sac, these organs are not very readily discernible. When one knows what to look for, however, and where to seek for them, they can generally be made out very distinctly after a little patient focussing. The rectal papillae are then seen to be glandular organs, composed of a soft fleshy substance of a light yellow colour, having the form of elon- gated cones, the bases of which are flat or very slightly rounded. Into the centre of the base of eacK. of the papillae there enters a small tracheal tube which ]3asses nearly to the extremity of the organ, where it bifurcates and turns backwards, terminating in very numerous and exceedingly minute fibrils, which permeate the entire substance of the organ. Similar delicate fibrils are also given off laterally from the main tracheal filaments in its course through the organ, radiating from the centre to the circumference, and ramify- ing in all directions throughout its structure. The external sur- faces of the papillae appear to be perfectly smooth, and 1 have been unable to make out the existence of any pores or orifices, except perhaps close to the extremities, where the surface seems irregular or warty, and I fancy that on one occasion, when examining a specimen under peculiarly favourable conditions, I was enabled to make out, with the iin. objective, about 10 or 12 orifices at the conical extremities of each of the papillae, and, in point of fact, there can be no doubt that some such orifices must exist whether I have been able really to -see them or not. The tracheal vessels which supply the six papillee all spring from one tracheal tube ex- ternal to the intestinal sac, the branches from which pass through its walls and serve to sujDport the papillse as they hang freely sus- pended within the sac. It is very interesting to watch the constant movements of these long conical finger-like papillae crossing and gliding over each other as the walls of the sac are pulled to one side or the other by the external muscles.

W. H. FURLOXGE OX THE PULEX IRRITAXS. 17

Tlie posterior extremity of the digestiye sac is connected either directly, or by a very short canal, with the anal orifice which opens just behind the pygidium.

Having thus described the structure of the alimentary and diges- tive canal, and the organs pertaining to it, so far as I have been able to make them out, I will now briefly recapitulate my views of their functions.

Tlie blood as ingested passes directly to the first stomach, which appears to perfomi the office of a crop, or receptacle for the food. In this organ it is, as we have seen, kept in a state of violent agita- tion, and is, I believe, constantly regurgitated into the gizzard, where it is submitted to the action of the corrugated iTibbing sur- faces of that organ, the blood corpuscules being thus broken down. From time to time, portions of the contents of the fii'st stomach are expelled through the valve at the posterior extremity of the stomach into the intestinal canal, connecting the two stomachs. I may obseiTe, in parenthesis, that 1 have frequently had an* opportunity of observing this passage of the contents of the first stomach into the second, and that the successive portions of the contents thus transferred, never rested in the connecting intestinal tube or gut, which is always enij)ty except at the moment when the food is passing through it into the second stomach. It is possible that some portion of the blood may be taken up by certain quasi absor- bent vessels with which the canal is seen to be lined, even in the course of the rapid passage I have described, but without doubt the chief portion of the assimilative process takes place in the second stomach. This appears to be proved by the fact that when the insect is permitted to gorge itself with food, it will, as already noticed,, fill both stomachs with blood, and, of course, the contents of each will present precisely the same appearances under the microscope ; but after the digestive process has gone on for some time, the con- tents of the second stomach (which, in the first instance, very speedily assume an opaque dark brown colour) become progres- sively lighter in tint, until at length the contents of the sac appear to consist of a limpid fluid of a light red or pink colour, in marked contrast with the deep crimson colour of the contents of the first stomach, which, I may remark, almost always retains its crimson colour so long as it remains in that organ. When the food has been so far digested, the insect emits small portions of the contents of the sac from time to time, as excreta, to make room for portions

JouRN. Q. M. C. Ko. 18. c

18 W. H. FURLONGE ON THE PULEX IRRITANS.

of fresh blood from the first stomach ; but, as before mentioned, ■when the creature has the opportunity of taking in an unlimited supply of food, it has the power of expelling the whole contents of the sac, which then becomes filled with fresh blood. This power of ejecting the contents of the second stomach in whole or in part at the will of the animal, explains the manner in which the female insect is enabled to make provision for the sustenance of the larva, when it emerges from the egg, as originally observed by the late Kichard Beck, by emitting portions of semi-digested food in small drops which immediately coagulate and form the food of the larva when hatched.

The Respiratory System. — We now pass on to the consideration of the organs of respiration, and I may premise by observing that I know of no creature in which the typical respiratory system of the insecta can be so admirably seen or so conveniently studied as in the Pulex. Mr. Lowne correctly remarked in the course of his observations upon my last paper, that when a living flea is immersed in glycerine and examined by reflected light, its tracheal system appears as if injected with mercury. But I think it may be even more beautifully shown, and certainly more advantageously studied, by transmitted light under the ^in. objective. Selecting a young and transparent specimen, which, for the purpose of observing the tracheal vessels to the best advantage should be kept without food for about 48 hours, in order that it may be compressed somewhat powerfully without injury, the employment of the ^in. objective reveals a structure of extraordinary beauty and wonderful complexity. I have attempted in the accompanying drawing to delineate the general form and course of the main tracheal vessels of the abdo- minal system, but it is simply impossible for the most accomplished and careful artist to do full justice to the subject, and the drawing now shown has no pretensions to be more than a mere sketch, simply intended to illustrate the description I am about to offer.

The principal portion of the respiratory system of the flea is seen to consist of two main tracheal vessels running along the entire length of the abdomen, just beneath the chitinous envelope on each side, and passing, as will be afterwards shown, into the thorax and head. At the posterior extremities, the upper and lower main tracheal vessels unite and communicate with those remarkable and very large trumpet-mouthed spiracular orifices, described in my previous paper as situated beneath the margins of the plates sur-

W. H. FURLONGE ON THE PULEX IRRITAXS. 19

rounding the pygidium, and opening on either side just in front of that organ. These large spiracles, in fact, appear to be the principal orifices by which the main tracheae are supplied with air. The lower main tracheae communicate with the external air by means of short branches, which, rising vertically, cross the upper main trachea, and terminate just beneath the cup or funnel-shaped ex- tremities of the round spiracles, described in my former paper as situated along the line of the abdomen.

It is very remarkable that there appears to be a complete break, or solution of continuity, between the extremities of all those spiracular orifices, and the tracheae which they supply, with the exception of one or two turns of the wire-like spiral fibre supporting the parietes of the tracheal tubes, and which may be seen to pass from the spiracle to the tracheal tube. I have endeavoured, by the use of very high powers and careful illumination, to comprehend this curious peculiarity of structure, and I have satisfied myself that there exists a very thin transparent membranous envelope, surrounding the trachea, and that at the points of junction with the extremities of the spiracles this membrane is expanded into a sort of bag or corrugated sac, as shown in the drawing, the obvious purpose of this method of union being to permit the flexure of the animal's body in every direction, without danger of rupturing the delicate tubes connected with the external spiracles.

The lower main tracheal vessel (B) presents the ajDpearance of a series of loops* hanging down between the tubes which communi- cate with the abdominal spiracles, and from the lower or convex sides of these loops a series of large tracheal vessels descend per- pendicularly, one of these vessels running downwards on each side of every segment of the abdomen. From these large vessels, as also from all parts of the main trachea, proceeds a wonderfully complex system of minor vessels, ramifying in every direction, and proceed- ing to every portion of the animal's organism in a series of filaments constantly decreasing in diameter, the ultimate fibrils being so minute as to demand the highest powers of the microscope to resolve, and yet the smallest of these vessels exhibits its characteristic spiral structure as perfectly as the largest of the main tracheae.

* It is proper to state that the so-called loops of the lower main tracheal vessel are shown much flatter than they are in reaHty. This is due to the distortion arising from the compression of the insect, which has the effect of elongating or stretcJung out this system of vessels. In their natural position the loops are much deeper and are closer together than is here depicted.

20 W. H. FURLONGE ON THE PULEX IRRITANS.

At the second abdominal spiracle, tlie two main tracheal vessels unite anteriorly and join the large trachea, which descends perpen- dicularly from the first spiracle, and thence, from a little above the point of junction, a large vessel — of course on each side of the animal — proceeds into the thorax and head, supplying the smaller vessels, which ramify from thqm to the various organs contained in these portions of the body of the insect.

I have here to refer to the pair of erectile spiracles mentioned in my former paper as situated in the epimeron of the mezo-thorax. It may be remembered that I described these as round dome or nipple-shaped prominences, capable of protrusion and retraction, and which, in fact, in the living animal are in a state of continual movement. Tracheal vessels may be distinctly traced as being in connection with and supplied by these erectile spiracles, and since the reading of my previous paper I have satisfied myself that the protrusion of these organs is not, as I believe was suggested, due to the compression of the insect while under examination, but that they normally present the characteristics I have described. I may add that though I have not been able to make them out, I confidently anticipate that similar pairs of spiracles exist in each segment of the thorax, and I would invite the assistance of some of our working members in searching for them. My reasons for this conjecture will be stated presently.

I also desire to refer to the remarkable sacs which I described as existing in the upper tarsal joints of the third pair of legs, and which I at that time considered to be contractile sacs. It may be remembered that Mr. Lowne demurred to this view of their struc- ture, and gave it as his opinion that these so-called sacs are really expansions of the tracheal vessels supplying the limbs. I think it right to say that I have since ascertained that Mr. Lowne's view is correct, and I now exhibit one of these tracheal enlargements carefully laid down by the aid of the neutral tint reflector. (Fig. 4.) I was led into the error of considering these vessels muscular sacs, from the fact of their rhythmical contractions, wdiich I sup- posed to be accomplished by muscular bands, for the striations of which I mistook the spiral fibrous structure of the tracheal vessel itself. Eut while I admit the error into wdiich I was betrayed, as to the structure of these so-called organs, I must adhere to the views I expressed as to their use and office, viz., that by the rhyth- mical compression of these tracheal enlargements — however that

W. H. FURLONGE ON THE TULEX IRRITANS. 21

is accomplished — the air is forced throiigli the infinitely less than capillary ultimate fibrils of the trache£e, and in this opinion Mr. Lowne coincides.

I am now brought to a few suggestive remarks which I desire to offer upon the functions of the wonderful respiratory apparatus just described, as a whole.

The problem to be solved is, in what way does this apparatus act in maintaining a constant and regular circulation of air through every tube and fibril of the air system ? It has been suggested that inspiration is accomplished by the dilation of the abdomen by voluntary muscular action, and conversely, that expiration is effected by corresponding muscular compression. But I would ask, is it by any means an ascertained fact that the air in- spired through the abdominal spiracles is expired through the same orifices ? I cannot venture to assert positively that it is otherwise, but I strongly incline to susjDect the probability that the air inspired through the abdominal spiracles may be expired through the spiracles of the thorax. The appearance and apparent action of the so-called erectile spiracles of the thorax seems, to my mind, to lend support to the idea, and it is from these considerations I have been led to suppose that similar spiracles will probably be found to exist in the other segments of the thorax.

I put these views forward as jourely suggestive, and with the hope of promoting enquiry and work, in a most important and in- teresting department of insect structure, upon which, I believe, our knowledge at the present time is very limited ; and I cannot help thinking that a collation of the knowledge possessed and a com- parison of the opinions entertained by individual members of our Club could not fail to throw much light upon the subject. I shall be very glad if the expression of these hypothetical views has the effect of inducing such a discussion, even should the result be (as is, indeed, very likely) to demolish the conjectures I have formed. May I be permitted to say that discussions of this character, con- ducted in the spirit of simple investigation and search for truth amongst our members, would infallibly result most beneficially to the progress of knowledge in those branches of science which we are incorporated for the express purpose of promoting.

The Beproductive System. — The structure of the reproductive organs of the female flea is comparatively simple ; that of the male is exceedingly complex and remarkable.

22 W. H. FURLONGE ON THE PULEX IRRITANS.

I shall first describe —

The Female Reproductive Organs. — The posterior lower abdominal plate of the female flea is elongated or produced on either side so as to form a V shaped recess projecting for some little distance be- yond the body of the insect (Fig. 5). These lateral projections, as we shall afterwards find, serve an important purpose during the congress of the sexes. From the margins of these plates a fringe of thick bristly hair projects inwards. The lower terminal portion of the fleshy part of the abdomen projects between these lateral plates, and upon its under side is situated a circular orifice fringed with two rows of short hairs projecting inwards and outwards. This orifice opens into a somewhat elongated vaginal canal, the direction of which is upwards and forward. In the unimpregnated insect, grape-like clusters of ovaries may be seen dependant from the walls of the enlarged extremity of the vaginal canal, through which, as will be afterwards seen, the male organ passes for its entire length, thereby bringing the seminal fluid into direct contact with the ovaries. After impregnation the walls of the ovarian cavity distend enormously, so as to contain from six to ten exceedingly large eggs, relatively speaking, which, when fully matured, appear to occupy more than one half of the capacity of the entire abdomen. The eggs of the flea are matured with great rapidity, and are produced at the rate of five or six per diem, when the insect is in a state of captivity ; but I have reason to believe that under natural condi- tions they are produced even more abundantly. I have not had opportunities of observing the development of the eggs in the ovaries from the time of impregnation to maturity, this being one of the points I have been obliged to leave unworked.

The Male Reproductive Organs, so far as I have been able to make them out, may be considered as consisting of three principal parts —

a. The prehensile organs and their sheath plates. i3. The sheath of the penis. 7. The penis.

Referring to Fig. 6, it will be seen that the inferior terminal plate of the male flea is elongated so as to form a deep cavity. On either side of this cavity are situated two rounded concavo-convex plates of chitin, somewhat thicker in substance than those envelop- ing the abdomen, but striated in a similar manner, the margins of

W. H. FURLONGE ON THE PULEX IRRITANS. 23

which are thickened and fringed with curved bristles projecting backwards. In their normal position these plates incline inwards towards each other, the convex sides being outwards, so that their fringed margins unite and form a ridge or crest, rising very little above the edges of the cavity, and completely closing the opening in which they are placed. These sheath plates gradually taper downwards like leaves, and terminate in stout short stalks, which are attached to curved chitinous bands similar to those after- wards to be described as moving the sheath of the penis. When these organs are in action they are pushed backwards and upwards, and assume an erect or nearly parallel position, as shown in the figure. This movement is accomplished by means of appropriate muscles attached to the chitinous processes just described.

The Prehensile Organs (Fig. 7) consist of a pair of strong claws, or nippers, situated within the concave sheath plates, to the stalks of which they appear to be attached, so that when the sheath plates are extruded the forceps come up with them. These organs strikingly resemble the terminal joints of the large claws of the lobster, excepting that one of the extremities of each is broad and square, while the other is bluntly pointed. They are composed of chitin of a deep reddish-brown colour, and appear to be solid or homogeneous in structure, and although attached to the stalks of their sheath plates, they are capable of independent movement in a manner precisely similar to that of the analogous terminal joint of the lobster's claw. I may observe that one of the plates, with its accompanying forceps, is sometimes extruded or retracted sooner than the other, though they generally move in unison.

The Sheath of the Penis. — When the plates and forceps have been protruded the sheath of the penis begins to emerge between them, and finally assumes a position nearly erect, or slightly curv- ing backwards, which, it may be remembered, was shown in the large drawing of the male pulex accompanying my previous paper. The sheath possesses a very remarkable structure. It consists of a fleshy organ, relatively of very considerable size, which is surrounded for about two-thirds of its circumference by a very thin, polished, curved plate of chitin, which serves to sustain the fleshy organ within, the posterior portion of which projects beyond the edges of the investing plate.

At the extremity of the organ, which is triangular in section, the terminal edges of the chitinous plate are capable of being drawn

24 W. H. FURLONGE ON THE PULEX IRRITANS.

inwards by the retraction of the fleshy organ to which it is attached forming flaps, of an inverted V shape, as shown in Fig. 10, or they may be expanded or opened out in a most extraordinary manner, presenting a notched or embattled outline or margin, in which posi- tion it is seen to be furnished with three curved spines, as shown in Fig. 9. The contraction and opening out of the extremity of the organ are accomplished very suddenly, and with considerable force.

The opposite or inferior extremity of the sheath is connected to a pair of bands, or rather rods, of dark brown chitin, which curve upwards and then backwards into a coil of several turns, like a spring, as, in fact, there can be no doubt is precisely the purpose which these curved and coiled rods really serve, extruding the penis sheath by uncoiling, and retracting it by the opposite action, the coiled state being the normal position of the rods.

The Penis. — Looking down upon the extremity of the extruded sheath, when expanded, a minute orifice may be observed through which the penis is projected. It is a dark -coloured, wire-like organ — presumably chitinous — which is capable of protrusion for about half the length of its sheath ; but of its structure I can give no further descrijDtion ; in fact, I have only seen the extrusion of the organ in some four or five instances out of the dozens of male fleas I have had under observation, and on these occasions it was protuded and retracted with such rapidity that the eyes could hardly follow it. I have no doubt, however, that it constitutes one of those coiled rods or chitinous fibres just described, and that it is projected by the uncoiling, and withdrawn by the release of the spring-like coil. I have been entirely unsuccessful in my attempts to distinguish the spermatic vessels of the male pulex, unless they may be certain glandular organs filled with transparent globules, situated around the spiral coil; but it is difficult, if not impossible, to distinguish any difference in structure between these and the or- dinary fatty globules abundantly found aglomerated together in many parts of the internal organs.

Having now described the organs of reproduction, it remains to describe their office. The first action is the extrusion of the sheath plates and forceps. These latter grasp the plates which, as already described, project on either side of the extremity of the abdomen of the female, and thereby the male is enabled to take firm hold of the female insect during copula. The extrusion of

W. H. FURLONGE ON THE TULEX IRRITANS. 25

the sheath of the penis then takes place, wliich next passes into the vaginal orifice.

I have repeatedly witnessed the copula of the insects, and though I have before referred to the pulex as an animal in which the typical structures and functions of the organs of insects can be studied under singularly favourable circumstances, I may here re- mark that in no description of investigation are these exceptional advantages so great as in the study of the reproductive process. When young and transparent specimens of the insect are selected this important process can be seen with remarkable clearness, and the animals being so closely locked together may be manipulated with great facility. Even when placed between the glasses of the compressor they will endure an amount of compression quite suffi- cient to render the abdomen of each insect perfectly transparent without the interruption of the copula. When thus examined the extremity of the sheath of the penis may be seen to be continually opening out and closing up, and by this action the spinous processes attached to the extremity of the sheath appear, as it were, to grasp the ovarian clusters I have described ; but I have not been able to observe the protrusion of the penis itself during the copula, nor at any time to distinguish spermatozoa in the female.

I would strongly urge that the members of the Club should re- peat these observations, when pr.obably much more than I have been able to make out would be discovered in this important department of insect physiology. It is by no means a difficult matter to in- duce copula in the pulex. Tn general it suffices to keep the male and female in separate tubes for a day or two, then to feed them, and afterwards to put them together. In most cases copula immediately ensues. Easy as it is, however, to make the observation, I have never yet met with any microscopist who has witnessed it, with the exception of one fellow worker, Mr. Mclntire, whose obBervations on the subject exactly confirmed my own. If he should happen to be present at the reading of this paper he will, perhaps, give the Club the benefit of his observations upon the subject.

I had intended to have closed my paper with a description of the development of the Qgg through its transformations into the per- fect insect, but I fear I have already trespassed upon the patience of the Club too much ; I hope at a future period, however, to read a short communication on this concluding portion of the life-history of the Pulex Irritans.

26

PROCEEDINGS

• December 8th, 1871. — Conversational Meeting.

The objects exhibited were: —

Muscular Fibre ... ... ... ... ... ... Dr. Ramsbotbam.

Melicerta ring ens ... ... ... ... ... W. H. Golding.

Fructification of Ferns ,,

Nerves of Teeth T.C.White.

December 22nd, 1871. — Chairman, Henry Lee, Esq., F.L.S., &c., Vice-President.

The following donations to the Club were announced : —

*' The Monthly Microscopical Journal" from the Publisher.

" Science Gossip" the Publisher.

" Proceedings of the Royal Society" the Society.

** Proceedings of the Literary and Philosophical) the Society.

Society of Manchester" J

*' The American Naturalist" in Exchange.

The thanks of the Club were unanimously voted to the donors.

The following gentlemen were balloted for and duly elected members of the Club : — Mr. Henry Lea, Mr. Daniel Ward, Mr. John Webber.

Mr. James Smith read a paper " On Cell Mounting," for which the thanks of the Club were returned.

The Chairman expressed his great satisfaction at the kind of paper read by Mr. Smith, and hoped that similar communications would be made more frequently than had lately been the case, for it should be borne iu mind one of the chief objects of the Club was to encourage intercourse between those who were seeking information on such subjects ; he felt he could not too strongly impress this upon the members. He fully appreciated the value of many of the papers which were read at the meetings, but notwithstanding this he was very desirous of seeing the meetings assume more of a conversa- tional character, and that the feeling should be encouraged that any member needing information could come there without being afraid to ask a question,

Mr. Mclntire inquired how Mr. Smith got the lead so perfectly smooth as it appeared in the specimens laid on the table ?

Mr. Smith replied that if the sheet lead was laid upon a plate of glass and then rubbed over with an ivory paper knife, it would become as perfectly smooth

27.

as could be required. Wlien the cells were cut out, by placing them between two ordinary glass slides, and applying a slight pressure, they could be made as flat as possibly could be. He might also add, that although those which he had described were square, yet rings might easily be cut out by using two punches of different sizes.

Dr. Matthews suggested that another method of flattening would be by rolling the lead out upon a sheet of stout plate glass with a piece of glass barometer tube, and he thought that by cross rolling the lead would be flattened better than by simply rubbing it with a ruler.

The Chairman observed that Dr. Bowerbank had used nothing else than common tea lead for his smaller cells for many years past, and for larger cells he used common plumbers' sheet lead. All his large collection of sponges were mounted in this way. It did not, perhaps, have a very neat appearance, b*t certainly answered the purpose very well. He believed that the doctor flattens out the lead on a board.

Mr. Smith said the cells were very easily made, so that two or three dozens of them could be made in the course of half an hour.

Mr. Richards said that some time ago he had to mount some wood sections, and procured for the purpose some rather light tin foil, which he cut out into cells with two punches, putting apiece of tube between them to keep them the right distance apart. A solution of glue and treacle was used for fixing them j this was laid on and allowed to dry first, and was found very useful in sticking on the thin glass covers, as it only needed a slight moisture to render it adhesive, whereas any liquid would have run under it and into so shallow a cell as the one he had described.

The Chairman remarked that this was carried out in a more perfect manner in the cells introduced by Mr. Sufi'olk.

Dr. Matthews said he found a difficulty in using these cells, because he could not fix them on with marine glue, which required a temperature so high to melt it that the tin cells were in danger of melting also.

The Chairman remarked that he used nothing else himself but marine glue to fix the tin cells to the slides, and it answered admirably.

Mr. Smith said his method was to fix them by running a ring of gold size upon the slide.

The Secretary said he was very much obliged to Mr. Smith for bringing this sub- ject before the meeting. For many years he had been in the habit of using cells made of a thin kind of lead known as "pattern lead, ' which was used by dentists for taking patterns for their gold plates. It would be found to answer the purpose very well, and had none of the objectionable qualities mentioned by Dr. Matthews, since the slide might be made almost red-hot without melting the cells, and the cells were very easily stuck on with marine glue. For shallow cells a simple ring of gold size, and gum dammar put on thickly and allowed to get hard, answered the purpose very well, and if Bastian's cement were used instead, the cell could easily be built up higher by adding layers upon those which had become dry. Another way was to use the zinc cells, which would stand any amount of heat; acid, however, would aff'ect these, but vulcanite cells would resist acids. In making cells for mounting in fluid, it would be found of great advantage to set up some standard size, and keep to it, as this would enable the worker in a short time to estimate correctly the exact amount of fluid required for filling — a matter of very much importance.

Mr. Leifchild asked if Mr. White considered the vulcanite cells to be the best ?

28

Mr. White said he thought they would be, where acids were used. Mr. Mclntire said that he had used the vulcanite cells, and found tliey had a tendency to chip off the slides after a time.

Mr. White thought this would very likely be the case, because if the slide were made too hot the vulcanite would melt ; but if not hot enough, the cement would not become sufficiently melted to make them adhere.

The Chairman proposed a vote of thanks to Mr. Smith for his communication, which was carried unanimously.

The Secretary, in announcing the meetings for the ensuing month, congratu- lated the members upon the fact that the Club would enter upon the new year 18/2 with 560 members upon its list.

The Chairman said he should be very glad to see a greater number of objects ealiibited at the close of the meetings; they added very much to the life of the conversaziones into which the meetings were then resolved, and he hoped that members would not forget this.

The proceedings then terminated with a conversazione, at which the following objects were exhibited : —

Proboscis of Vanessa by Mr. Bevington.

Vaginecola (species) Mr. Bucknall.

Poison Fang of Viper Mr. Tafe.

Circn\a,tion in Anacharis Alsinastmvi ... ... Mr. Geo. Williams.

Attendance— Members, 62 ; visitors, 3.

January 12th, 1872. — Conversational Meeting.

The objects exhibited were: —

Istlimia eneo'vis W. H. Golding,

Ear of Frog injected (polai-ised) M. de Guimaraens

Calcareous plates round mouth of Echinus ... J.G.Waller.

Skin, &c., of Star Fish „

Skin of Eay , all palarized , ,

Cate?nceZZa (Australian Zoophyte) S. J. Mclntire.

Section of Crystalline Lens from eye of Haddock,

i-in. obj ,

Vorticella microstoma ... ... ... ... ... Geo. Williams.

Rotifer vidgaris ,,

Section of Tooth of Cape Ant-Eater Mr Gibson.

Parasite of Water Eat Dr. Ramsbotham.

CeWs of C-^ddis worm (Phryganea) ,,

Yonng of Asterina gibhosa T.C.White.

Attendance— 37 members, 2 visitors.

A. Smith.

January 2Gtli, 1872. — Chairman, Dr. Lionel S. Beale, F.R.S., &c., President.

The following donations to the Club were announced : —

Land and Water" (weekly) from the Edi or.

'The Monthly IMicroscopical Journal" the Publisher.

Science Gossip " the Publisher.

The Popular Science Review" the Publisher.

29

*' Proceedings of the Manchester Literary andPhilo-) ,-, o ■ i

sophical Society " ... ) ' ■

*' The American Naturalist" in exchange,

" Journal of the London Institution " ... the Librarian.

A 2in. Objective Mr. Kowlett.

The thanks of the Club were unanimously voted to the donors.

The following gentlemen were balloted for and duly elected members of the Club :— Mr. Edwin Denyer, Vr. Eobert Hudson, F.E.S., Dr. J. Hamilton MeKechnie, Mr. Edwin Tulley Newton, and Mr. Frederick George Hilton Price.

The President regretted to have to announce that there was no paper to be read that evening, but several gentlemen had communications to make to the Club.

Mr. James Smith made some observations explanatory of improvements to^a new substage for the microscope, which he recently introduced to the notice of the members. The stage, as now constructed, was exhibited and described, and a vote of thanks was passed to Mr. Smith for his communication.

Dr. Matthews said that most of the members of the Club would, no doubt, recollect that he had produced a self- centring turn-table, about a year ago (May 27th, 1870), and exhibited it at one of the meetings. It was then pronounced to be excellent, and it remained excellent for new slides, but in most cabinets there occurred a necessity for revarnishiug old slides, and cells on these were not always found to be central. In such cases this turn-table would only correctly centre them, and thereby show their eccentricity, and its accuracy thus became a defect, although it was a defect consequent upon its perfection. He had, how- ever, now devised a remedy for this by dividing the top of the table into two portions, so arranged, that by sliding the upper part upon the surface of the lower, any required degree of eccentricity could be attained. This was accom- plished very easily and simply, and he thought that the arrangement rendered the turn-table as perfect as could be desired; certainly he did not himself see what more could be done to it. One of the improved turn-tables was then ex- hibited to the meeting, and its utility shown by centring a slide which had been eccentrically mounted for the purpose.

The President said that Dr. Matthews had exhibited a very practical arrange- ment, and one which certainly rendered his ingenious turn-table as perfect as could possibly be.

Mr. T. Curties said that Mr. Aylward, of Manchester, had sent two things to the meeting that evening for exhibition. One was a triple nose-piece of his own construction, and which appeared to be more successfully made than many of those in common use ; it centred the objectives very easily, and worked smoothly and well. The other was a contrivance devised for the purpose of getting objects out of reach. It consisted of a pair of forceps and a cutter, arranged so as to be fixed at the end of a stick, and having two strings attached, one of which, on being pulled, closed the forceps, and thus held the object last, whilst the other worked the cutter and severed it.

The President proposed votes of thanks to those gentlemen who had favoured the meeting with their communications, and also called attention to the 2in. objective which had that evening been presented to the Club by Mr Rowlett, for use with the tank microscope which belonged to them. This power was of ex- cellent quality, and was one of Mr. liowlett's own manufacture.

The Secretary anr.ounced that it had been decided to hold the annual soiree of the club on the 15th of March, and it was further intimated that the Com- mittee had decided that members who had not paid their subscriptions ought

30

not in fairness to Lave soiree tickets sent to them, a decision whicli was greeted with applause and unmistakable signs of satisfaction by the members present.

Seven gentlemen having been proposed for membership, the proceedings ter- minated with a conversazione, at which the following objects were exhibited : —

Triple nose-piece and cutting forceps, for collecting "i by Mr. Aylward, of

sticks ...

Parasite of Elephant

Legs of Curculio

Surface markings on Triceratium and Isthmia enervis

Anystis Cursoria

Melkerta ringens {alive)

Memhranipora pilosa

JFibro-cellular tissue of Catasetum tridentatum ... Ei'ecting arrangement adapted for dissection, &c.,

with Binocular Microscope

Pleurosigma formosum

Cyclosis in Anacharis

^cidium EuphorhicB

Wing of Moth

Injected toe of Mouse

Injected ear of White Mouse

Manchester. Mr. T. Curties. Mr. Duck. Mr. Green. Mr. de Guimaraens.

Mr. Hainworth. Mr. Jackson.

Mr. Oxley.

Mr. Eichards. Mr. J. Eussell. Mr. Sigsworth. Mr. Jas. Smith. Mr. A. Topping. Mr. A.Waller.

Attendance — Members, 96 ; visitors, 10.

February 9th, 1872. — Conversational Meeting.

The following objects were exhibited : —

Sponge, Geodia Bo.rettii H. F. Hailes.

Tingis foliacea Mr. Allbon.

Markings of Diatoms with high powers — opaque Mr, Green.

Fly's Tongue Mr. Eichards.

Transverse section of small intestine of Cat ... Mr. Topping.

Cinnabar Crystals in Chalcedony Mr. Gibson.

Hydra, Volvox, Stentors, &c. Mr. Martinelli.

Astromma Aristotelis A.Waller.

Cigroryiyzaflaveola Geo. Williams.

February 2ord, 1872. — Chairman, Dr. R. Braithwaite, F.L.S., &c., Vice-President.

The following donations to the Club were announced : —

*' Land and Water" (weekly) from the Editor.

"The Monthly Microscopical Journal" the Publisher.

*' Science Gossip" the Publisher.

' ' The A merican Naturalist" in Exchange .

*'The Proceedings of the Literary and Philosophical")

Society of Manchester" J the Society.

" The Invisible World," by Dr. Mantell Mr. C S. Bentley.

The thanks of the Club were voted to the donors.

The following gentlemen were balloted for and duly elected members of the Club :— Mr. A. Atkins, M.E.CS., Mr. A. Atkins, junr., L.E.C.P., the Eev. Thos. Henry Brown, Mr. Alexander Colvin, Mr. Theodore Charles Izod, Dr. W. E. Grindley Pearce, Mr. C E. Stevens.

31

The Secretary read to the meeting the second portion of a paper by Mr. Fur- longue, " On the minute Anatomy of the Flea" (Pulex Irritans), illustrated by diagrams.

The Chairman proposed a very cordial vote of thanks to Mr. Furlonge for his very interesting paper. To have all the details of such a subject laid before them, so as to be read at any time, would be of great service. He hoped that other members of the Club would be induced to follow Mr. Furlonge's example, and carefully follow up some one subject in the same manner. There were many other insects about which it would be very desirable to know more. The bug, for example, would furnish a subject, and there were also many other fleas beside the one which formed the subject of the paper which had been read, such as the flea of the dog, cat, mole, fowl, and others, each of which had some peculiarities to distinguish it.

A vote of thanks to Mr. Furlonge was then put to the meeting and carried unanimously.

Mr. S. J. Mclntire said that, being unprepared for it, he was rather surprised that his remarks had been quoted by Mr. Furlonge in his paper, and that he should now be called upon to repeat them. Mr. Furlonge merely asked him some time ago if he had ever witnessed the copula of fleas, and he replied that he had. At the time he was studying these insects he happened to have caught one — a female — and put it into a test tube. Soon afterwards he caught another, and put it into the tube also ; it proved to be a male flea, and they at once began copulating. The curious part of it was that the female got on the top of the male, and the male organ was turned round quite over his back to reach the female. With regard to other kinds of fleas, those of the mouse were very in- teresting ; they were very pretty little things, and were apparently blind. The largest flea in the world was that obtained from the Australian ant-eater. It was as large as a small-sized pea.

The Chairman said that the observation made by Mr. J. Mclntire accounted for the enormous development of the penis in the male flea.

The Secretary said that he happened the other day to get out the gizzard of the flea, but he could not make out the corrugated bands referred to in Mr. Furlonge's paper. He saw, however, a number of bristles, which appeared to him to take the place of the teeth found in the gizzard of the cockroach and cricliet.

Mr. Topping confirmed the observation of Mr. White, and said that if the gizzard were opened and laid out the bristles would be readily seen j if the gizzard of the dog-flea were examined it would be found Jifi'erent.

Mr. Oxley said that he had also observed the bristles alluded to by Mr. White.

Mr. Matthews introduced to the meeting a portable case and stand for a microscope lamp. He thought that persons were generally disirous of diminish- ing the weight of their accessory apparatus, as well as that of their instruments, and endeavoured to dispense with as many pieces as possible. He had in this instance attempted to meet this desire by dispensing with the ring, stand, and upright supporting rod, and making the case itself into a support and stand. This was accomplished by making grooves in the sides of the interior of the case, into which a wood shelf supporting the lamp was made to slide. This simple contrivance he had found to answer perfectly; the grooves were ^in. apart, and the lamp was quite steady even when the top groove was used. When the shelf and lamp were placed at the bottom of the case, the door could be shut, and the case conveniently carried about by means of a brass bail handle. The lamp was one of Mr. How's, with an earthen chimney, and the only inconvenience he had found arose from the great heat radiated from the chimney. He had, there-

32

fore, sought to obviate this by clothing the chimney with felt, and found it to answer the purpose very well. The box itself absorbed some of the heat, and the felt so far absorbed the rest that no inconvenience could now be said to arise from that source. The felt was sewn on round the top of the chimney, and fixed at the bottom by a piece of coiled watch-spring, the chimney being too hard to pierce through. The case and lamp could be supplied complete at a cost of 17s. 6d. or I83.

The Chairman thought these contrivances very ingenious, and expressed the obligation of the Club to Dr. Matthews for bringing them before their notice.

Mr. Green intimated that he had taken the opportunity of bringing the lime light to the last gossip meeting, and the unanimous opinion of those members who saw the diatoms illuminated by it was in accordance with the description given in his paper. The hemispherical dots were particularly high in Hippo- campus ; in Formosum there was evidently a flattened surface, and this was still more so in Angulatuni. It should be remembered that there was no covering glass over the specimens, neither were they seen through any other medium, and when shown thus in their natural condition by transmitted light as opaque objects, the "file marks" were seen to be unquestionable depressions. In this contro- versy, as in some others, it might be said that the opinions of both sides seemed to be true. In order that those members who were not present on the occasion when he exhibited the diatoms before might have an opportunity of seeing and judging for themselves, he had again brought the lime light with him, and should be happy to exhibit the objects at the close of the meeting.

The proceedings then terminated with a conversazione, at which the following objects were exhibited : —

Wiug of Jloqyho Menelaics by Mr. Golding.

Unmounted Diatoms, illuminated as opaque objects,by ^ the lime light

Injected Skin of Frog Mj. de Guimaraens.

Fungus Leaf of Coleus Mr. Jackson.

Confervse Mr. Martinelli.

Tongue of Blow-Fly .. Mr Eichards.

Antennae of Lace Wing Fly Mr. Sigsworth.

Transverse Section of Ox-tongue Mr. J. A. Smith.

Heliopelta metii Mr. Geo. Williams.

Attendance — Members, 89 j visitors, 11.

R. T. Lewis.

f Mr. Green .

March 8th, 1872. — Conversational Meeting.

The following objects were exhibited x—

Red Earth Mite Mr. Fitch.

V(\\\g of Pterofliorus -pcntadactylus... Mr, Ward.

Chdex annulata, Large Winged Gnat Geo. Williams.

Various Lichens W. H. Golding.

Parasite of Ox H. E. Freeman.

Australian Polyzoa, &c E. P. Pett.

Echinus Spines ,,

Thyamis femoralis, Gyqss Flea F. W, Andrew.

Various Echinus Spines in Section Mr. Gibson.

Anthers of Mallow Mr. Sigsworth.

Attendance— 63 members, 6 visitors.

33

On Cutting Cells.

Bj James Smith.

(Bead 22nd December, 1871.;

In the above diagram 1 have endeavoured to indicate a very simple, but I think, at the same time, very accurate way of cutting out cells for mounting Microscopic objects. The material I have employed is the lead used for lining tea chests ; the advantages of this were pointed out to me some time ago by Dr. Bowerbank, who has, I believe, used it for some time as a material for making cells. It is very readily obtainable from any grocer ; can be had of several degrees of thickness, and, from its extreme pliability, can be very readily flattened out or moulded into any required shape, and I think that, without disparaging any other substances employed in cell making, that this sheet lead will be found useful for many kinds of mounting, and the readiness with which it can be obtained makes it all the more desirable, A piece of lead having been obtained, and properly smoothed out; slips of — say 1 inch in breadth, and any convenient length may be cut off, and being marked with small lines (or dots) as above, as a guide for placing the punches in cutting, two or more cells may be cut out of each other with great accuracy and very little trouble. In the above diagram four punches are supposed to be used, namely — a 1 inch, I inch, ^ inch, and ^ inch punch ; and, as will be seen from the diagram, twelve cells of three different sizes are thus cut from the small strip of lead represented. It is scarcely necessary to say that this method of cutting will do equally well for other materials used in cell making.

JouRN. Q M. C. No. 19. D

34

On the Measurement of the Working Focal Length of Object- Glasses, and their Magnifying Power.

By G. West Roybton-Pigott, M.A., M.D., Cantab , M.R.C.P., M.R.I., Fellow of the Cambridge Philosopbical, tlie Royal Astronomical and Microscopical Societies, late Fellow of St. Peter's College, Cambridge.

Though strange, it is nevertheless true, that two observers, with the same eyepiece and objective, do not always see an object magni- fied to the same amplitude. A change of focus may be necessary. A short-sighted person sees the virtual image of the magnified object at a distance of perhaps six inches ; the long-sighted adjusts it perhaps at twelve or even eighteen inches ; the distinct plane of vision, called the field of view, is variably placed according to the focal length of the eye of the observer, and therefore at distances of considerable variety. Under these circumstances, if two ob- servers, the one very short, and the other very long-sighted, both agree to observe together, their powers of vision proportionably vary. It is necessary, then, to fix a standard for estimation. Most persons can see distinctly at ten inches distance. In this case the power of any lens at this distance is found by dividing ten by the focal length / or

Magnifying power =^10 -f- focal length/

or=^orlO -T-/.

To persons unread in optical principles, there appears some little difficulty in understanding the variable foci of a lens, and I may, perhaps, be excused for introducing the following illustration, known I believe to very few working opticians : — If we take a lens (say 3 inches focus), and form the image of a candle (or much better, the image of a small perforation in a brass plate placed before it) upon a sheet of white paper, it is well known that as you move the candle from the lens you must move up the paper towards it, in order to obtain a clear image. Now, the special point which I wish to bring before the notice of the members of the Quekett Club is

G. WEST ROYSTON-PIGOTT ON OBJECT GLASSES.

35

this, that exactly at the position where the image is formed clearly at the same distance from the paper as the candle is, the distance between the candle and image is the least possible or a minimum. A most useful result is now obtained ; in every case this minimum distance is exactly four times the focal length of the lens. In the case of a three-inch lens this mijiimum image distance will be found to be exactly 12 inches.

We will now suppose that instead of the three-inch lens a two- inch objective is used in precisely the same way. The minimum image distance between a candle and its image will be found much less than 8 inches, so that the real focal length* is 1-J^f or rather less than one inch and a half.

There are two or three preliminary points which may not be uninteresting. To find the focal length of a plano-convex lens, turn the/«^ side to the sun, and measure the exact distance from the sharpest image on a card to the convex surface.

If the lens be equiconvex, half the thickness must be added.

If the lens be used as a convexo-plane, and the plane side is towards the image, when the aberration is reduced, two-thirds of the thickness must be added.

The minimum image-distance avoids these inconveniences of measurement altogether.

In every case the true focal length will be more accurately determined by using only a small central aperture applied to the lens in question.

I have designed an instrument of considerable accuracy for measuring the focal length of ordinary lenses, consisting of a per- forated metal plate, and a white screen or piece of ground glass, with a carrier for the object-glass or lens. By means of a long screw tapped with similar right-handed and left-handed dies, the perforated plate and lamp and the screen are simultaneously made to approach or recede from the lens, which is thus kept always exactly equidistant from the plate and from the screen. The lens to be measured being fixed, the screw is turned, until an exact image is formed upon the screen, of the perforations ; one- fourth of the distance between them is exactly the focal length required. I term this instrament a Focimeter.

But in the case of very minute lenses, considerable difficulty is

* Focal point of a lens is generally known to be the focus of parallel rays.

d2

36 G. WEST ROYSTON-PIGOTT ON OBJECT GLASSES.

exj^erienced in finding their exact focal length by measurement of their curves. In this case, the focal length can be obtained most readily by the following artifice. If the magnifying power be great, a stage micrometer is to be placed exactly at ten inches dis- tance from the ground glass screen. If a microscope be used, by taking out the field and eye-glasses of the eye -pieces, an ordinary circular 1-lOOth micrometer may be inserted ; then replacing the eye-lens only, the image of the stage micrometer must be accurately observed, and the magnitude of a 1-lOOth nicely determined in the divisions of the eye-piece micrometer. Suppose this to be (??2), the actual focal length of the lens in question will be found for small lenses as follows : —

Divide ten by this number (m), increased by two.* Larger lenses will require a correction to be hereafter explained.

Exarnple. — A small lens is found to magnify a hundredth of an inch upon the stage to measure 35 hundredths at 10 inches distance from the stage, within the field of an eye-piece, deprived of its field lens. Find the focal length ; also for a piano convex find the curva- ture of the tool to grind the lens.

N = 2>b. /=10 -i-(ii + 2) = 10^37 == 0"-27027 nearly.

In a piano convex lens radius of curvature for flint — = i focal length = 0''- 135 13 inches.-f

Example 2. — A compound lens forming an object glass of great power enlarges the thousandth of an inch to 158 divisions in lOOOths, as before at 10 inches. Find the approximate focal length. Here

/= 10 -r- (158 -h 2)= 10 -^ 160 = At

* In a paper contributed to the " Philosophical Transactions," March, 1870, I showed that this number (m), or the number of times the image is magnified by the lens, is equal to i? — 2, for small lenses, or ?/i = ^ — 2 ; whence f = —^

f If perfect accuracy is required the number m (35) should be increased by the reciprocal of m, namely, gU ; and the distance to be then divided not by 35 -I- 2, but by 35 -i- 2 + -3I5, or 37-028571, which gives

0"-270062, instead of 0"-27027 inches. X Most pei'sons will find a difficulty in reading 158 thousandths, or 15"8 hundredths, on the eye micrometer ; indeed, they would more nearly read 160.

The decimal change for the omission of the reciprocal i.^g in the divisor, which ought accurately to be 158 •\-2-\- -jl^, is very slight. Performing the operation, 158 + 2-1- il^, for a new divisor = 1600063291.

/= 10 H- (160-0063291) = 0062497 nearly Now ,'e =0-062500

DifPerence = "000003 Wliich is less than the 10,000th of an each. So that when Powell and Lealands fg magnifies 1600 times with a C eye-piece of one inch focal length, it is accurately Veth focal length within an almost inappreciable quantity.

G. WEST ROYSTON-PIGOTT ON OBJECT GLASSES.

37

From this it appears that an exact sixteenth should produce an image precisely 158 times as large when the object is exactly ten inches from the field of the eye-lens at the stop of the eye- piece.

For practical purposes, therefore, an eye-lens magnifying ten times would enlarge the object in this case 1,580 times. Now a C eye-piece of Powell and Lealand is just equivalent to an one-inch lens ; therefore, when these makers announce their sixteenth to magnify 1,600 times with a C eye-piece, this objective is nearly the yi-g- of an inch focal length within a small decimal.

The magnifying power employed at any moment is often so great a desideratum, and yet so unattainable (when one is closely engaged in some delicate investigation, and using a variety of objectives), without great loss of time, that the following observations upon a simple method exhibited at the meeting of the Fellows of the Royal Microscopical Society last month, may, it is hoped, prove acceptable. Having met with many persons and some opticians who experienced a difficulty in understanding the reason of the thing, I trust that the preceding remarks will clear the difficulty away.

If we settle it as an axiom for very high powers, such as the -J-th and yV^h, that at ten inches distance of the stop of an eye-piece, without the field -glass, the enlargement of thousandths on the stage will give the focal length simply by dividing ten by the amplifica- tion increased by two, then it is evident that by using a single lens of one-inch focal length magnifying ten times, if we count how many hundredths of an inch in the stop correspond to a hundredth on the stage micrometer, ten times that amount with an inch or C eye- piece is the magnifying power. Now replace the field-lens (usually of 3-ihch focus) for an eye-piece of 2-inch focal length, having an eye-lens of one inch, the magnifying power will be reduced con- siderably in the proportion shewn by the new reading. Whatever object glass is now used, and whatev-er length of tube happens to be in use, so long as the eye-lens is 1-inch focal length, teji times the apparent amplification of the stage micrometer will give the power under employment.

I keep an eye-piece (two-inch) with one-inch, eye lens, armed with a glass micrometer, ready for use. Every microscopist should demand that the optician mark the focal length of each of his eye-pieces. Powell and Lealand's C eye-piece is exactly one- inch focal length ; and at the usual distance of ten inches the power of any object glass with it is at once found by multiplying the re-

38 G. WEST ROYSTONPIGOTT ON OBJECT GLASSES.

cii^rocal of the focal length (eight is the reciprocal of ^) by one

hundred.

The standard rule by which nominal " inches," " quarters,"

*' eighths," '' sixteenths," and " twentieths " are constructed is

therefore most properly taken, so that with a C eye-piece of one

inch focal length and the stop of the eye-piece being exactly ten

Jjiches from the stage, their respective magnifying powers shall be : —

(Objectives) ... Incli Quarter Eighth Sixteenth Twentieth (Powers) 100 400 800 1,600 2,000

I have fomid Nobert's lines to form very beautiful stage micro- meters ; but as they are fractions of the Paris line, observations with them require laborious reduction to the English standard. But I wish to acknowledge here the kindness of Mr. Baker, the optician, in placing at my disposal Jackson's own beautifully ruled micrometer lines, 2,000 to the inch. With the aid of this, and a micrometer in the stop of the eye-piece, I found the powe?' of Powell and Lealand's new l, with a one inch Kellner of Browning's make and searcher (with a fine definition), to be 5,250 diameters.

Without searcher and one-inch eye- piece : —

nearly

Andrew Ross . . . 1851 . "quarter" . power, 540 = ^th.

Wray 1870 . one-fifth . power, 540*

Jiesume.

I. — The focal length of a lens is one-fourth the least distance between image and object at which it can be distinctly formed.

II. — If a distance of ten inches between object and image be taken (to simplify the calculation), and the amplification measured for a division, then in the case of small lenses the focal length is found by dividing ten by the divisor increased by two.

III. — The magnifying power of an object glass for any length of tube can be ascertained by using an eye-lens of one-inch focal length, with or without a field lens, by measuring the amplification of a stage micrometer upon another placed in the stop of the eye- piece, and then multiplying it by ten.

IV. — Different eye-pieces being compared by the Camera Lucida, or marked in focal length by the maker, all other powers are im- mediately ascertained by the simple rule of proportion. |

* The actual focal length = 10 -i- (54 + 2 + J:,) = 10 ^ (56' 0185) ; or a power of 540 represents a focal length about 2-lOOths of an inch less than a true ^.

t A half -inch eye-piece will of course be twice the power of the inch, and so forth.

39

Upon a Phenomenon of Monocular Vision in Connection with THE Delineation of Microscopic Objects.

By W. H. FURLONGE.

(Read April 26th, 1872.;

There are few departments of manipulation of greater importance to the working microscopist than the means of delineating, with accuracy and rapidity, the objects which, from time to time, are brought under his notice. Facility in drawing from the object as seen in the microscope, by the unaided eye, is a comparatively rare accomplishment, and even where there exists a natural artistic aptitude, it is only by long practice, and after many painful failures, that such facility can be attained. Hence the value of what may be termed mechanical aids in the delineation of objects, such as the Camera Lucida, and other forms of reflecting prisms, the steel disc, and the neutral tint reflector.

It is not my purpose to enter into the respective merits of these and other methods of microscopic drawing, but to bring under the notice of the Club a phenomenon of vision connected with the employment of the last-named instrument — the neutral tint re- flector— which appears to me very remarkable, and deserving of further investigation, not solely because of its interest in connection with mental, nervous, or brain impressions, but also on account of its bearing upon practical working facility in microscopic drawing.

We are all familiar with the neutral tint reflector, and with the optical principles involved in its construction. As usually made, this instrument is furnished with several reflecting glasses of different depths of colour, to adapt it for use with an illumination of greater or less intensity. Even with such appliances, however, we are most of us aware that it is a matter of some difficulty to obtain the best balance between the illumination of the object in the microscope, and that of the paper upon which the drawing is to

40 W. H. FURLONGE ON MONOCULAR VISION.

be made, and that to produce the best effect it is necessary to screen the jDaper from too bright a light.

8ome months since, in attempting to accomplish this adjustment, I chanced to hit upon a singularly happy illumination of the paper, by means of which I was enabled to trace the object under obser- vation with more than ordinary facility. On removing my eye from the instrument, however, I was greatly surprised to find that in shading my drawing paper to produce the best effect, I had actually interposed the margin of the screen between the observing eye and the drawing-paper. I had thus completely cut off all possibility of vision of the reflected image through the neutral tint glass with the observing eye ; yet the apparent projection of the image upon the paper was seen with increased distinctness. Repeated experi- ments only served to confirm the reality of this singular pheno- menon of vision, and to prove that the best mode of using the reflector as a drawing instrument was to employ a piece of glass which had been made perfectly opaque by the application to its under surface of a thick coating of black varnish, such as asphaltum, instead of the transparent neutral tinted glass.

Now let us consider the rationale of this curious fact. It will be at once perceived that we must entirely modify the views hitherto held as to the principles upon which we are enabled to perceive the image reflected by the neutral tint — and, in fact, by every other form of reflector — upon the paper on which we draw. These principles I take to be, that the pencils of light forming the image in the microscope are reflected into the observing eye, which, look- ing through the transparent reflecting glass, sees the image appa- rently projected upon the drawing-paper beneath — the office of the non-observing eye being to direct the point of the pencil while the object is being traced. But the experiment I have described proves that the observing eye does not see through the reflecting glass at all, and that in reality it is the non-observing eye — that is the eye which is not looking into the instrument — that perceives the image, and is called upon simultaneously to direct the pencil. This at once explains the difficulty we all feel, more or less, in keeping the point of the pencil constantly in view, and why it is that in tracing an object we are so continually and provokingly losing sight either of the pencil or of the object.

I do not propose here to enter upon the somewhat abstruse enquiry, how the mental impression conveyed to the brain by one

W. H. FURLONGE ON MONOCULAR VISION. 41

eye is seen by the other apparently projected upon the drawing- pajDer on which it is looking. In fact, the question appears to me to belong more to psychology, or at all events to the most recondite physiological considerations of reflex nervous impressions, than to practical microscopy. It is very probable, however, that some of our members, and notably our President, are capable of throwing light upon the cause of this remarkable phenomenon, which it would be very desirable to obtain. My present object is simply to bring the fact itself before the Club, to point out its practical bear- ing upon our every-day work, and to suggest to some of our in- genious mechanical members, who may have the time to devote to the investigation, that it may be very possible to improve the brilliancy of the image projected on the paper, and consequently to increase the facility in tracing it, by the substitution of a very truly and highly-polished plane metallic speculum, for the opaque glass reflector I have described.

The late Mons. A. de Brebisson.

One of the Foreign corresponding members of the Club, Mons. Alphonse de Brebisson, of Falaise, Normandy, died on the 26th April last, at the advanced age of 74 years. His large and valuable collection of some thousands of slides of Diatomaceas is to be disposed of by his son, M. Bene de Brebisson.

42

Observations on the Fresh-water Sponges.

By J. G. Waller.

(Read April 26th, 1872.;

On the Fresli -water Sponges more has been written, than on any other genus of this order of the Protozoa. This may be accounted for in the ease with which they are found, and in consequence their examination involves but little difficulty. It is not, therefore, my intention to aim at anything like completeness, but strictly to con- fine myself to that which the title of my paper suggests, viz., " Observations." This relieves me from the dangerous temptation to theorise, and thus I believe I shall do my duty best to myself and to you. I shall divide my task into two parts. In the first I shall give a general glance at the organisms under consideration, then a series of observations carried on with the growing sponge during three months, in which time I made drawings and memor- anda daily, illustrating every change which took place.

The two Fresh-water Sponges, known in England, are dis- tinguished as " Spongilla lacustris," and " Spongilla fluviatilis," literally the Lake and the River Sponge. These terms were given by Dr. Johnston, and are now generally accepted. Though they are thus distinguished, they may often be found growing in the same locality, under the same conditions, and within a few feet of each other.

The two are strikingly dissimilar, and yet their characteristics have been often confounded. S. lacustris grows in long, lobular, branching forms ; S. jluviatilis in large masses, without symmetry. Yet it has been asserted, that the latter is also found with lobular projections, and Dr. Bowerbank suggests that this may be due to it having originally been parasitic on some Alga. I have myself seen several examples of this form, but arrive at quite another conclusion. At least, in those instances which have come under my observation, this was certainly not the cause, but a confervoid

J. G. WALLER ON FRESH-WATER SPONGES. 43

growth, overlaying and ojDpressing the sponge, constrained its de- velopment in the usual way, and the lobular growth was in such places as were free from this parasitic obstruction. As soon, how- ever, as the sponge escapes this its tendency to spread laterally is manifested, and the terminations of the lobes widen. I believe this is a weakly condition of the sponge, only seen in young examples, and not under healthier circumstances.

The external character, then, of the two is entirely dissimilar when mature and fully developed. Colour is a very variable cha- racter, dependant so much upon light, but, in general, S. lacustris is of a dark green, whilst that of S. Jluviatilis varies from a dull yellow to an emerald tint. More intimate examination makes the distinction between them still wider. The membranes of S. lacustris are covered with minute spiniferous spicula, whilst those of the other have none. The structure of the skeletons are similar, but coarser in the former than in the latter. Their spicula have but slight differences ; and whilst on this part of my subject, I must call at- tention to what is somewhat remarkable — that in both these sponges a form of spiculum has entirely been overlooked by those eminent observers who have done so much to instruct us on this interest- ing group of organisms.

Dr. Bowerbank, in his work on the British Spongiadse, which must now be regarded as the text-book on Sponges, gives only one form of spicula as belonging to the skeleton of either of the British Spongilla. That of S. fluviatilis he calls " Acerate," that of S. lacustris " Subfusiform Acerate." As regards the first, if you take a mature example of the sponge and make a vertical section, mount it in balsam and examine it under the microscope, you will find that nearly the whole of the spicula are spiniferous , the plain '' Acerate " form being very few in number. But now make a horizontal section, and examine it in a similar manner, and then the spiniferous form is found to be few in number, the greater part being that which Dr. Bowerbank has described. This at once shows us the true position each occupies in the skeleton, and that there are two forms is without doubt. The question now arises how this form could possibly be overlooked if it be constant. I am not sure if I have always seen it myself — and I have seen a slide sold as " Spicules of S. Jluviatilis,^^ in which it certainly did not apjoear ; nevertheless, I am inclined to think it a constant characteristic in mature examples. In *S'. lacustris the spiniferous spicule does not

44 J. G. WALLER ON FRESH-WATER SPONGES.

constitute more than 6 or 7 per cent, of its skeleton, and it is somewhat shorter than the others. The next point of dissimi- larity between them is in the structure of the ovaria, so far as re- gards the sjDicula of the integument.

The bi-rotulate form of S. Jluviatilis must be known to every microscopist, as it is so frequently figured in works on the Micro- scope. Those of S. lacustris are totally different, being similar in character, though smaller, to those of its membranes, but varying in their curvatures to such an extent that I have occasionally seen them taking that of a complete circle. The preparation of the ovaria showing the spicula is extremely easy. There is no necessity for any boiling in nitric acid, as recommended by Dr. Bowerbank, but a section of the sponge containing them needs only to be steeped in strong spirits of turpentine for a few days, and then mounted in balsam to show their structure completely, and it is the more interesting as they are seen in situ.

There is another characteristic of the latter sponge which ob- servers have not failed to note, i. e., the numerous abnormal forms of spiculum which are found in it. But, indeed, they are quite as numerous in S. Jluviatilis, and they are so far worth our notice when they seem to play into shapes, which in other sponges are constant. But I will now pass from these somewhat dry details to matters of more interest.

In the early part of November, 1870, accompanied by a friend, I went into Hampton Lock, in search of the Fresh-water Sponges, and returned home laden with a rich gathering of, as I thought, both species. But it entirely consisted of S. Jluviatilis, the lobular form of which deceived me, as I took it to be S. lacustris. On reaching home and submitting a portion to examination, I found it was pouring out a yelky substance of a dirty white colour, which proved to consist of myriads of ova. These had a tendency to aggregate together in masses upon the slide, perhaps by the law of attraction, but in some cases these masses immediately threw out a membranous projection like the pseudopodia of the Amoeba, which they closely resembled ; and I regret that I was not able just then, for want of leisure, to follow up any subsequent development. After setting aside some pieces of the sponge as specimens, a few fragments were left in the gathering bottle. This soon became exceedingly offensive and perfectly black with decomj)Osition. In a few days, however, purification ensued in the usual manner ; I

J. G. WALLER ON FRESH-WATER SPONGES. 45

filled up the bottle with fresh water and set it aside out of the direct light, where it remained all the winter. About the middle of March^ 1871, I examined it, and observed a green spot on a fragment of the old sponge left in the autumn. On applying a lens to the side, I was delighted to find it was a young sponge developing its mem- branes upon it. Considering the decomposition to which I have referred, I did not expect such a result.

But instead of giving an account of this, which was some- what advanced in development, I will select another example, which I found as a minute white speck upon the side of the bottle, thereby rendering it easy of examination. It consisted entirely of a pel- lucid membrane, supported or strengthened by spicula which projected slightly from its surface, enclosing denser granular matter, in which the pores could easily be detected by an inch objective. The osculum was remarkably developed, but being situated on the other side of the sponge was not always visible ; yet I had frequent opportunities of examining this curious organ. It was a transparent tube, generally somewhat larger at its distal extremity, often very long in proportion to the mass of sponge when fully extended, corrugated in structure and frequently having upon its surface a spiculum here and there without any order. One end of the sponge was attached to an ovarian capsule, divested of its outer integument and spicula. This served throughout my obser- vations as a pointer, for, being a fixed object, it indicated the nature of the changes, both of position and of form, which took place from day to day. These are difficult to describe, but will be un- derstood by aid of the accompanying figures, selected from the numerous drawings made.

Plate iii. Fig. 1 represents the sponge when first discovered, May 18. The following show the successive changes according to dates annexed : — Fig. 2, May 25 ; Fig. 3, May 31 ; Fig. 4, June 7 ; Fig. 5, June 10 ; Fig. 6, June 12 ; Fig. 7, June 15 ; Fig. 8, June 17. The last shows the condition just before it separated.

The nature of the development was a contraction, so that the flat membranous expansion was drawn by degrees into another shape, denser in character, and gradually taking a globular form. During this process some of the external spicula of its network were left upon the sides of the glass ; and on the 7th day after my observations began a faint tinge of green was visible in the central portion. This colour increased daily with the progress of con-

46 J. G. WALLER ON FRESH-WATER SPONGES.

traction, and the density of the organism ; the projecting osculum was withdrawn, and in three weeks disappeared, leaving in its place a large opening or depression, which was very variable in size and appearance even on the same day. The sponge now assumed an ovate character, having a smooth surface, and no projecting spicula except at one end. From this it passed step by step into a globular form of a deep emerald green colour ; its attachment to the capsule became smaller and smaller, until at length it broke away, and disappeared (Fig. 8).

Now this was exactly the course which every other specimen fol- lowed. All from an expanded membrane, covering granular matter, contracted into a globular shape, then separated from its attachment, and disappeared. The only difference being that colour was acquired in other instances, whilst it was still expanding and growing upon the old sponge, and some were larger than others. Every indivi- dual, if such an expression can be correctly applied, had one osculum projected from it, and on this interesting organ I will add a few more remarks. Dr. Bowerbank states that this pellucid tube " exists only during the course of the energetic excurrent action." As far as I have observed this was not exactly the case. By re- ference to Plate iii. you will perceive two conditions in the same example. In Fig. 1 the sponge is active, the dermal membrane is fully extended, supported, as it were, at the apices of the spicula, and reminding one of a tarpauline over a hay-rick. Here the osculum is firm and erect. In the passive state the membrane is contracted, the osculum hangs down in a flaccid state, and the sponge is evidently at rest (Fig. 2). I found if the sponge was disturbed it went directly into this condition, and I fancied, upon one or two occasions, a dull and heavy day produced the same effect. The corrugated structure of this organ shows that the power of contraction and expansion must exist to a great extent ; but I never saw any absolute withdrawal of it, except under the conditions mentioned.

The phenomena, I have endeavoured to describe, seem to point to an act of gemmation with which we are familiarised in many of the lower orders of animal life, and which are well known to take place in, probably, every sponge ; and yet these are great differences from our usual experience. Here it is clearly a young sponge which gradually assumes this ajDpearance. It is well, therefore, to follow up the ensuing stage if possible, and happily this I am

J. a. WALLER ON FRESH-WATER SPONGES. 47

enabled to do. Previous to the observation thus recorded, I had one with a gemmule (?) already perfected, which I discovered em- bedded within the network of a piece of old sponge. It had evi- dently passed through the stages I have mentioned, and had now found a resting place for further development. I placed it in a zoophyte trough, supplying it constantly with fresh water, and ob- served it to be enveloped in a transparent membrane, defended or strengthened by a few spicula. It was sub-globular in shape, and of a bright emerald green colour (Fig. 3). I watched it daily. New membrane was forming about it on the network of the old sponge, and upon this new spicula (Fig. 4). This latter process was interesting. First one was projected, another extended from its apex, then one transversely. Additions were then made to the first parallel to it (See Fig. 5), and so forth.

Meanwhile the gemmule (?) was gradually increasing in size, swelling out and becoming more ovate, and its granular character more distinctly visible through the expanding membrane ; and having been nearly a fortnight under observation, began now to break up. The envelope burst, and its contents, consisting of minute masses of sarcode, which, when aggregated together, had an am^biform appearance, issued slowly from it (Fig. 6). Some of them settled upon portions of the membrane of the sponge, or upon the spicular network, and began to develope upon it. But by far the greater quantity became effete, as, perhaps, the condi- tions of life were little favourable for any further progress.

During my observations I saw upon several occasions minute bodies, ovate in shape, and having filiform appendages, moving about on the edges of the protruding granular masses, with a singular twitching motion ; but I could not bring a power of more than 60 diameters to bear upon them, and hesitate to express my belief in their being spermatazoids, which are asserted to have been seen by more than one observer, but which fact nevertheless remains in obscurity.

I have spoken of the phenomena described as of *' gemmation " and the product as a gemmule, yielding in this to appearances rather than believing the terms to be correct. A gemmule has been described as " a vital mass separated from the parent, and capable of being ultimately developed into a single individual, pos- sessing the same specific characters and capabilities as the present mass." But this clearly must be understood of those acts which

48 J. G. WALLER ON FRESH-WATER SPONGES.

are familiar to us in many organisms in an adult and matured con- dition. Here it is evidently not of that character, but is a stage of growth belonging to the young sponge, which may fairly be pre- sumed to have commenced from one or more ova. In the in- stance here given, we have the sponge actually developed upon the ovarian capsule, and in immediate proximity to the foramen, through which the ova pass out, and was clearly in the earliest stage of development. It appears to me that the phenomena rather show an analogy to the encysted state observed in so many of the lower organisms, and had a resemblance in its result to what I witnessed in Actinophrys Sol.* This question I leave for others to decide, and hope there may be amongst our friends those whose experience may help us to a conclusion.

Of the food of the Fresh-water Sponges we know but little, yet, if we may judge from the abundance of diatomacese frequently seen upon their tissues, they at least must fonn a part of it. The fol- lowing is a list of those varieties I have found upon the membranes and other portions of S. lacustris.

Pleurosigma attenuata Cymbella gastroides Navicula cuspidata „ cuspidata

Meloseira nummuloides „ boekii

Pinnul tria major Surirella biseriata

Cocconeis transversalis Amphora ovalis Campylodiscus spiralis „ membranacea

Cymatopleura solea Encyonema prostratum, &c., &c. ,, elliptica

I must, however, mention that the sides of Hampton Lock, whence my specimen was taken, are so rich in Diatomacese as to look as if covered with treacle ; and it would, therefore, be rather a marvel if we did not find some upon the membranes and other parts of a sponge growing in that locality.

* See Article on the Conjugation of Actinopliys Sol.

49

ANNUAL SOIREE.

March 15th, 1872.

The Annual Soiree was held, by permission of the Council, at University College, Go wer Street. Two hundred and sixteen microscopes were exhibited by Members of the Club, of the Croydon Microscopical Club, the South London Microscopical Club, the Forest Hill Microscopical Club, and the Metropolitan Opticians.

ACKLAND, T. G.y

ackland, w.,

Allbon, W.j

Andrew, A. E. Andrew, F. W.,

3 J

Atkinson, J.,

Bentley, C. S., Bevington, Thos., Bevington, W. a.. Bishop, W., Bonella, John, Braithwaite, R., M

Burr, T.W.,F.E.A

Burt, C. W., Cocks, W. G.,

Crisp, J. S.,

Crisp, — Crook, T.,

CURTIES, T.,

EXHIBITIONS BY MEMBERS.

File of Cricket, Acheta domestica.

Cinchonidine under polarized light, by a new form of selenite stage.

Tongue of Lamb.

Intestine of Ourang Outang.

Anguirtaria spatulata.

Leaves of Alyssum montanum.

Hypersthene, a mineral from North America.

Foot of Blow Fly.

Section of Shell (Haliotls).

Tongue of the Bee.

Tongue of Butterfly, Vanessa urticce.

A water wood-louse, Oniscm aquatilis.

Sori of several Exotic Ferns. D., Coralline with animals expanded.

Structure of Flowers, Asariim EuropcBuin and Thuja orient alls. S., Table polariscope with selenite designs, and unannealed

Photograms of the Moon in the Mici'oscope. Young Spider. Co7iochiltos. Volvox glohator. Melicerta ringens. Achromatic Stereoscope, with views tinted by coloured

reflectors. Malca sylcestris (4-inch), Lavatero. riihra (ditto). Spine of Echinus. Melicerta ringeris. Angninaria spatulata on Sea Weed, with Diatoms in situ.

JouRN. Q. M. C. No. 19.

£

50

Gushing, Thos.. Daintrey, G.,

Deane, — DoBsoN, H. H., Duck, W. A., Fitch, F.,

Fryer, G. H,

55

furneaux, j. r.j Gardiner, G.,

55

Garnham, J., Gay, F. W.,

George, E.,

Gibson, J. F., GOLDING, W. H.,

55

Gray, H. J., Gregory, John, Guimaraens, a. de

55

Hailes, H. F., Hainworth, W.

55

Hind, F. H. P., hopkinson, j., Hovenden, C. W., Hovenden, Fred., How, Jas.,

Ingpen, Jno. E., Jackson B. D.,

55

Johnson, J. A., Kiddle, E.,

Collection of Natural Flowers.

Selected Diatomaceae.

Section of Skin of Cat.

Polycystina.

Vibrio fritici, the cockles or purples of corn.

Section of Pearl.

Tongue and Lancets of a Fly (TahanusJ.

Volvox glohator.

Stephanoceros Eichhornii.

Ciliary action in Tadpole.

Spiders and Eggs hatching.

Hydra viridis.

Scales of Fern.

Coiieatus Taniarici.

Section of Whalebone, polarized.

Human Muscle injected.

Nudibranchiate Mollusc.

Emhletonia Orayi.

Lophopus crystallvius.

Fructification of Mosses.

,, Polytrichmn aloides.

,, Atrichum tmdulatum.

„ Hypnum.

Male flower of Polytrichum. Coneeptacles of Marchantia polymorpha. Section of Aberdeen Granite polarized. Arborescent Crystals of Silver and Gold. Elytron of Diamond Beetle. Leaf of Correa, stellate hairs. Petal of Correa stricta. , Acari of Eabbit, Listrophorus gibhis. $ . $ . Sea Horse, Hippocampus brevirostris. Chelifer. Volvox glohator. Water Fleas, Baplinia. Gold Dust from Australia. Young Oysters, Ostrea edidis. Marine Algse, Polysiphonia fastigiafa. Foraminifera from the Atlantic Ocean, 2,000 fathoms. Palate of Loligo vulgaris. Spicules of Gorgonia. Palate of Haliotis tuberculata. Nummulites Icevigatus. Absorption spectrum of Chlorophyll. Winged seed of Cybibtax. Volvox glohator. Blossom of Yew Tree. Eggs of Parasite of Eeeves' Pheasant. Seed of Nemesia versicolor. Drawings of Ancient Egyptian Jewellery. Photographs in Abyssinia, Magdala, &c.

51

Lee, Henry, F.L.S. LooF, S. A., LoY, W. T., McIntire, S. J.,

Marttnelllt, a., Meacher, J. W.,

Nelson, Jas., Newton, E. T.,

northey, m. d., Perry, F. J., Quick, G. E.,

Eeeves, W. W.,

Robins, Edmund, Rogers, J., Rogers, J. R.,

Rogers, T.,

Russell, T. D.,

SiGSWORTH, J. C.

Slade, J., Smith, A.,

Smith, Jas.,

Marine Algse, Pohjsiphonia urceolata, witli capsules.

Elytron of Diamond Beetle.

Section of Blow Fly.

Wing of Saagala gloriosa, a moth from Central America.

Flea, Pulexirritans (alive), and Red Spider, Trombidium.

Electric Spark discharged between Graphite terminals.

Heart of Water Snail, Planorhis X 56.

Tank Life (Sfentor, &c.)

Reseda odorata.

Fioiaria hygrometrica.

Bellis perennis.

Melicerta rmc/ens.

Eye of Frog, nerves of the cornea, stained with chloride

of gold. Scale of Perch polarized. Weevil, Coiieatus Tamarasi. Head of Gnat. Gizzard of Cockroach. Tongue of Butterfly. Section of Human Kidney. Transverse section of Rush. Photograph of Shrewsbury Cathedral. Batracliospermum monoliformef var. pulclierrimuon, a

Confervoid Alga from Devon. A selection of Spicules of Gorgonacese, illuminated by

the new Pocket Lamp and portable microscope body. Gemmules of Sponge. Wings of the Gnat Crystals by Polarized Light. Citric Acid, Cane Sugar, Sugar of Milk, Maple Sugar,

&c. Polycystina, Astromma Aristotelis. Anguinaria spatulata, Epistylus.

Hydra viridis and H. vulgaris. Circulation in Anacharis. Collections of British Stalk-eyed Crustacea and Echino-

dermata. Sepiostaire (Cuttle Fish), horizontal and vertical sec- tions. Flower of Common Mallow deprived of the Corolla,

showing the Monadelphous Stamens with Anthers

and Pollen. Freshwater Polyzoa, LopJiopus crystallinvs. Capsule of Ceratodon purpureus. Porphyrine, section. Fossil Foraminifera from cavity in flint. Spider, alive. Cheese Mites. Head of Hornet. Cockchafer.

52

Smith, J. A., Lai'va of Ephemera, or Day Fly, polarized.

Circulation in leg of Water Louse, polarized. Red Water Spider. Lily of the Valley. Fibres of Flax, Limim usitatissimum, by Polarized

Light. Rotifera and Entomostraca, alive. Bird's Eye Tobacco. African and other Limpets, and Oysters. Flea, Pidex irritans. Leaf of Pomaderris a^jetala. Polyxemis lagurus. Degeeria Nicoletii, Degeeria cincta. Pond Life, Hydra viridis. Pencil Tail, Polyxenus lagurus. Sphagnum or Bog Moss. Pond Life {Vorticellce). Artificial Crystals of Hippuric Acid under Polarized

Light. The Pulsation of the Heart and Circulation of the Blood

in young Salmon. Illustration of Pond Life (Entomostraca). Section of Nose of Mouse (injected). Section of Spine of Echinus, polarized. Elytron of Diamond Beetle. Cuticle of Equisetum sylvaticum. V Lepidodendron > Transverse Section of Specimens figured

in the " Monthly Microscopical Journal," for Feby., 1872). jj Pitchstone from Arran.

Mr. Holmes, of 477, Oxford Street, exhibited his patent stereoscopic binocular m'croscope, which appeared to interest and elicit approval from the members present.

The following opticians also exhibited microscopes, &c.:— Messrs. Bailey, Baker, R. and J. Beck, Mogiuie, Murray and Heath, Powell and Lealand, Ross, J. H. Steward, and Swift.

Mr. T. D. Russell exhibited a Natural History Collection ; Mr. Ernest Swain, Fossils ; Mr. E. Kiddle, some facsimile Drawings of Ancient Jewellery of a date 1800 years B.C. ; Mr. Rockfort Connor, some Microscopical Drawings of various Yegetable and Animal Tissues.

The London Stereoscopic Company exhibited on the screen some views of various places of interest, illustrating South Africa and the Livingstone Expedi- tion, in the Mathematica,l Theatre. Mr. Apps exhibited Electrical Experiments in Vacuo, such as Gassiott's Cascades, &c., &c. Mr. How exhibited Micro-pho- tographs and Photographic Views by the Lime Light, varied by the new form of Kaleidoscope as applied to the Lantern.

Smith, W., Stickstone, C. W. Suffolk, W. T.,

Swain, Ernest,

Tafe, J. F., Terry, J., Ward, F. H.,

Warrington, H, R., Westbrooke, Edwd., White, F. W.,

White, T. C ,

Williams, Geo.,

Wright, E , Young, John T

53

PROCEEDINGS.

March 22nd, 1872. — Chairman — Dr. John Matthews.

The following donations to tlie Club were announced : — •

" The Monthly Microscopical Journal " from the Publisher.

" Science Gossip " ,,

"The Lena" \ the State Microscopical

' Society of Illinois.

*' The American Naturalist " in exchange.

" The Journal of the Loudon Institution " ...from the Librarian. " The Annual Eeport and Proceedings of the ) ...

^ Geologists' Association" J the Association.

* ' The Proceedings of the Literary and Philo- \ -u a ■

sophical Society of Manchester " ... * the Society.

" The 22ud Annual Eeport of the Bank of) ,, ^ ^ „

England Library" 1 Mr. Suffolk.

" Conspectus of Diatomacese," extracted from ) Professor Hamilton Smith.

" The Lens," 4 Nos j

The thanks of the Club were unanimously voted to the donors.

The following gentlemen were balloted for and duly elected members of the Club:— Mr. George Daintrey, Mr. Joseph Guyton, Mr. Ernest D. Marquand, Mr. R. H. Pinker, Mr. C. S. Rolfe, Mr. Harry Smurt.

A Paper by Dr. G. W.Royston Pigott, ''On a New Method of Ascertaining the Magnifying Power of Objectives," was communicated to the meeting by the Secretary.

The Chairman said there could hardly be a more fertile subject for discussion than that which was the subject of this papc'-, neither was it possible to over- rate its importance, seeing that accuracy of measurement lay at the very foun- dation of microscopical investigation. He had himself found very little difficulty in ascertaining the magnifying power of any objective by means of a little con- trivance of his own— the calliper eye-piece — which was introduced to the notice of the Club soon after he had first brought it out, and the use of which he ex- plained at the time. He felt sure that all the members would join most cordially in presenting a vote of thanks to Dr. Pigott for his paper, especially as they would have the privilege of reading it in extetuo when printed in the Journal.

The Secretary, in seconding a vote of thanks to Dr. Pigott, drew the atten- tion of the members to the simple method of ascertaining the magnifying power of objectives mentioned by Dr. Beale in his book on the microscope.

A vote of thanks to Dr. Pigott for his paper was then put to the meeting and carried unanimously.

54

Mr. Green intimated that he had again brought with him his lime light for the purpose of exhibiting his Podura Scale as an opaque object, and he desired to thank several gentlemen who had assisted him in his investigations. Mr. Arthur Cole, of Liverpool, had in a most kind manner sent him some slides very beautifully mounted, and Mr. Topping had also very kindly supplied him with the Podura scales.

The proceedings then terminated with a conversazione, at which the following objects were exhibited : —

Sarirel la gemma by Mr. Curteis.

Podura Scales, shewn as opaque objects by the lime light Mr. Green.

Injected Muscle of Cat Mr. de Gaimaraens.

Eectal Papillae and Gizzard of Flea Mr. Mclntire.

Euglena viridis Mr. Martinelli.

Selection of Gorgonia Spicules Mr Eichards.

Injected Lung of Frog Mr. Topping.

Attendance — Members, 55 ; visitors, 8.

EicHARD T. Lewis.

April 12th, 1872. — Conversational Meeting.

Objects exhibited: —

Trachea from Larva of Dytiscus by Mr. Geo. Williams.

Larva of the Gnat Mr. J. A. Smith.

Gizzard of Mole Cricket "^ ivr n i

Wing of Earwig 3 * ^'

Phillipine Foraminifera Mr. Hailes.

Spines and Plates, Synapta similis ... ) ^^ ^ r^

Gizzard and Stomach of Cricket ... j ^^^- ^^ G^^^araens,

Amphioxus paradoxus Mr. Slade.

Section of Sarsaparilla Mr. Sigsworth.

Meridion circulare Mr. J. G. Waller.

Injected ova of Toad, transparent Mr. Topping.

Decomposed Glass Mr. Eichards.

Hippuric Acid '. Mr. T. C. White.

Selected Diatoms Mr. CoUam.

Convallaria Arcellum, &c,, &c. Dr. Ramsbottom.

Heliopelta, &c Mr. Jaques.

Cup Moss ... Dr. Matthews.

Section of diseased Canine Tooth ,,

Scales of Culex maculipeunis Mr. F. H. Ward.

Specimens of crushed quartz and crushed flint, to show the facility with which polarized light discriminates between sand consisting of comminuted quartz and sand consisting of comminuted flint. As examples : —

Sand from River Parrett, Somerset. Principally quartz j about 1 per cent, of flint.

Sand from site of the New Law Courts. Principally quartz ; about 1 per cent, of flint.

Lower Bagshot sand from Hampstead Heath. Contains no flint ; principally quartz and oxide of iron.

55

Chert from Portlandian beds, showing the same structure as flint.

Sand collected from a road repaired with flint. Consists principally of flint.

Sand, Blackfoot loam, from Charlton, Kent. Principally quartz, with about 1 per cent, of flint.

Thanet sand from Reculvers. Principally quartz ; about 1 per c(mt. of flint.

Chalcedony from Iceland, showing it to be crystalline silica, bearing the same relation to quartz crystal and massive quartz that fibrous gypsum does to selenite and common gypsum.

Chalcedony from Iceland.

Chalcedonic pseudomorph, showing rotary polarization, by W. Hawkins Johnson.

Present 59 members.

April 26th, 1872.— Chairman, Dr. R. Braithwaite, F.L.S., Vice-President.

The following donations to the Club were announced : —

" Science Gossip " from the Publisher.

*' The Monthly MicroscopicalJournal " ... ,,

** The Popular Science Review" j?

" The Proceedings of the British Naturalists' ") ^.^^ Society

Society" ... ... ^

"The first Report of the South London Mi-) , ^, ,

croscopical and Natural History Club " ^ " The Journal of the London Institution " ... the Librarian.

One Slide Mr. T. Rogers.

The thanks of the Club were voted to the donors.

The following gentlemen were balloted for and duly elected members of the Club:— Mr. Herbert Curwen, Dr. R. E. Dudgeon, Mr. J. W. Goodinge, Rev. William Law, Mr. S. H. Roberts, and Mr. Edward Tozer.

Mr. J. G. Waller read a paper, entitled ' ' Observations on Fresh Water Sponges," illustrating the subject by diagrams.

The Chairman proposed a vote of thanks to Mr, Waller for his interesting paper, and invited observations from gentlemen present. The vote of thanks Was carried unanimously.

Mr. Charles Stewart said that he feared he had lost a great deal of Mr. Waller's paper owing to the acoustic properties of the room, but he understood him to lay considerable stress upon the external forms of these sponges as a means of identification. He was himself more acquainted with the salt water sponges, and what he knew of these would lead him to judge that mere external form would be itself only a very rough and uncertain method upon which to form a decision. He should also rather fancy that the process which Mr. Waller had described, together with the flaccid condition, was perhaps due to to the condi- tion of the water in which the sponge was, so to speak, endeavouring to grow, although it could hardly succeed in managing it.

Mr. Holmes inquired whether Mr. Waller had observed any cilia on those little bodies which he had mentioned ?

5G

Mr. Waller, in reply, said that lie liad not observed any cilia, and that the raotion itself was very slow. He thought Mr. Stewart had misunderstood him in thinking that be relied upon external form as a means of identification. The flaccid condition of the osculum to which Mr. Stewart had also referred was not due to any cause such as had been suggested, for whenever he tested it by touching the sponge he found that it immediately assumed the other condition ; and he had taken great care to keep the water perfectly pure at all times during the course of his observations.

The Secretary read a paper by Mr. Furlonge ' * Ou a Phenomenon of Binocular Vision in the Delineation of Microscopical Objects."

The Chairman, in moving a vote of thanks to Mr. Furlonge for his communi- cation, expressed his regret at the absence of the President, who would, doubt- less, have been able to give some opinion upon the subject.

Mr. B. T. Lowne said that having previously paid some attention to the subject he thought he could do something to explain this very strange delusion, for it certainly was a delusion. In drawing an object with the neutral tint re- flector, the image was really seen on the reflector, but it appeared to be just as far behind it as the object itself actually was in front of it ; and it would, of course, be seen whether the light was cut off behind the reflector or not, and it would matter not at all whether with the observing eye they saw tlu ough the reflector or not, the apparent position of the image would be just the same. That a picture could be drawn in the manner described he would admit, be- cause it would be seen, apparently, on the paper with one eye, whilst the other eye would see the paper and the pencil, — the paper and the image thus seeming to occupy the same place. But in that case great care must be taken not to move the axis of either eye, otherwise the pencil and the object would seem to be continually running away from each other. As the reflector was very close to the eye the image would be moved a very little, although quite enough to cause a confusion of outlines. It was, however, most preposterous to suppose that the image went in at one eye and came out at the other ! When an object was drawn through the reflector the observer looked straight through and did not alter the axis of the eye at all, and there was then no difiiculty in keepin/ the pencil upon the image throughout. The ease with which a person could draw with both eyes in the manner described merely depended upon the ease with which he could squint. He should not, certainly, advise anyone to draw objects in this way, because to do so he must squint, and this would be almost sure in the end to damage the eyesight.

Mr. Unwin said that he had repeatedly drawn an object with the wrong eye when he had been too indolent to arrange the illumination properly. He thought that in doing so he must move the eyes about, but this did not matter so long as the axis of the eyes were kept parallel, or rather, in drawing with both eyes they must always make the image and draAving coincide. He did not know that in doing this he squinted. His experience was that when he used both eyes he did not draw so correctly as he did the other way, and that if he drew the object first with one eye and then, without moving, afterwards drew it with the other, he got two drawings.

Mr. Charles Stewart said that ou one point he must disagree, and that was as to the eyes being parallel ; their axes must, of course, converge. In drawing, as in observing, it was of advantage to keep the left eye open as well as the right, not necessarily for the purpose of seeing with it, but to relieve it fi'om the strain experienced when keeping it shut.

57

Mr. Lowne quite concurred with Mr. Stewart ; as to the eflFects in both eases, it, of course, amounted to the same thing, whether the eye was closed or whether it was not used, and there could be no doubt but that it greatly relieved the eyes to have both open when working with a microscope having a single tube. There were two things which might happen when drawing with botli eyes — it might happen that both eyes would be converged upon the same object at the same angle, but it would more usually be done by a squint. There was another thing which also occurred to him, namely, that the foci of the two eyes would have to be different, and this would be sure to cause very great fatigue to the eyes. Their axes must, of course, convei'ge, they could not possibly be parallel, and the question was at what angles did they converge ?

Mr. Tafe remarked that there was a convergence of the eyes both in looking through a microscope and in reading a book, and asked whether there was any difference between the two cases ?

Dr. Sansom said there could be no doubt but that there was a difference between the convergence of the eyes in drawing as described, and in reading — in the former case the axis of the eye would be a right line, or, rather, the perpendicular line of a right angled triangle, whilst that of the other eye would be its hypotheneuse ; and this would not be the case in reading a book.

Mr. Mainworth inquired whether there would be some 'variation according to the power used ?

The Chairman thought there might be a little.

Mr. Tafe asked whether the angle at which objects were seen would not render the binocular microscope injurious to the eyes ?

Dr. Sansom said that the angle would be so slight when using the binocular that it amounted to practically nothing.

Mr. E. P. Williams said that if he looked at the image through the neutral tint reflector, and then took it away and substituted an opaque reflector, then when he examined the image on the paper he could not see that there was any difference in the angle ; and he could not see that he squinted at all. He might also mention that once he introduced a piece of paper on the stage of tbe microscope where he could see it with the non-observing eye, and he drew the object in this way.

Mr. Mclntire said that this was the method which he generally adopted in drawing objects, but he was quite conscious that in doing so he squinted.

Mr. Lowne said that as some gentlemen did not seem to understand what squinting was he would just explain it, for be was sorry there should be any misapprehension. It was squinting when two objects were seen under such an angle of convergence as to make them overlap, as described by one speaker, — squinting was when one eye looked straightforward and the other looked at an angle either inward or outward. With regard to drawing upon the stage of the microscope, he had often done it, but should certainly do it no more, because it could not be done without a squint, and he could not squint without injuring the eyes. In looking through the binocular microscope the angle was really very little indeed, because the image was not seen by looking ^A,o?(^A the object- glass, but only at a picture in the eye-piece of the microscope. It must not be thought that a person looked down the tubes through the object glass, for if this was the case the binocular microscope would be a very painful institution, and would very speedily have to be put out of use.

Mr. R. P. Williams said that he did not regard it as a squint at all.

Mr. Lowue was sorry anyone should go away with a wrong impression, but

58

assured them that there was really a very great diflference between the two

Mr. Mclntire said that with regard to the binocular he believed the image seen was formed upon the field lens of the eye-piece.

Mr. Unwin exhibited and described an adaptation of the Nachet revolving stage to the mechanical stage of his own microscope, which, he believed, would be found of great utility. Having found the position of the stage in which it was concentric with the objective, and fixed it there, he removed the brass stage plate and substituted a Nachet stage . The advantages gained by being able to do this were pointed out^ and it was suggested that it would be very useful to microscopists if makers would determine the concentric position of the stage, and mark it by drilling a hole through the plates when in that position, so that it might be retained there, if required, by passing a pin through the hole.

Mr. T. C. White brought for distribution some sticks of cement, made of bees' wax and resin in equal parts, and melted together, and which he recom- mended as being very useful in securing glass covers, &c., temporarily when collecting ; it was readily melted by heat, and could be applied without further preparation on the spot.

The proceedings terminated with a conversazione, at which the following objects were exhibited : —

Spicules of Hyalonema mirabilis Arrenurus viridis (?)

Cellularia avieularia

Bone of Hippocampus "> Quartz Crystals ^

Hydra vulgaris (alive) ")

Larva of Ephemera (alive) •>

Snail Spawn on Water Cress

Scales on leaf of Heretiera littoralis

Arcyria

Tracheal System of Flea

Section of Spongilla fluviatilis and S. lacustris Ctenoid Scales of Sole

by Mr. Curties. Mr. Fitch. Mr. Golding.

Mr. Guimaraens.

Mr. Hainworth.

Mr. Martinelli.

Mr. Pett.

Mr. Slade.

Mr, Unwin.

Mr. Waller.

Mr. Geo. Williams.

Attendance — Members, 80 ; Visitors, 12.

May 10th, 1872. — Conversational Meeting.

Dlatomacese, Fragilaria Capucina

Section of leaf stalk Water Lily

Head of a Vanessa Butterfly ... Marine Life

Spiders Hatching of themselves Living Micro-lepidoptera

Section of a Blue Pearl found in a Mussel

Larvae of Gnat and

Lagena sulcata ...

Pond Life. Arcellum, Tabellaria, &c.

Sections of Echinus Spines. Acrocladia trigouaria, &c.

Section of Spinal Cord of Sheep, stained

Mr,	. Geo. Williams
Mr. Oxley.
Mr	. Golding.
Mr.	T. C. White.
Mr.	Fitch.
Mr.	, J. Smith.
Mr.	, Topping.
Mr.	Ward.
Dr.	Ramsbottom.
Mr.	J. Matthews.
Mr.	E. T. Newton.

59

May 24th, 1872.^ — Chairman, Dr. R. Braithwate, F.L.S., &c., Vice-President.

The following donations to the Club were announced : —

*' The Monthly MicroscopicalJournal " from the Publisher.

" Science Gossip " the Publisher.

" Proceedings of the Eoyal Society," Nos. 132-3 ... the Society.

'* The American Naturalist," for March and April in Exchange.

" Proceedings of the Geologists' Association" ... the Association.

" Proceedings of the Literary and Philosophical") the Society

Society of Manchester," for March and April J

"The Lens" in Exchange.

" The Journal of the London Institution " the Librarian.

" The President's Address and the Reports, &c., of a

the West Kent Natural History, Microscopical, > the Society,

and Photographic Society " )

12 slides Mr. John Eogers.

The thanks of the Club were unanimously voted to the donors.

The following gentlemen were balloted for and unanimously elected members of the Club :— Mr. W. H. Bennett, Mr. George J. Burch, Mr. Ernest Hinton, Mr, W. H. P. Sheehy, Mr. Ernest Schloesser, Mr. Henry E. Symons, F.R.M.S., Mr. Henry L. Sequeira, M.R.CS.

Dr. John Matthews called the attention of the members to a contrivance of his own, of which he had given some hint at the ordinary meeting of the club in March last. On that occasion, it would be remembered that a paper was read on behalf of Dr. Pigott, descriptive of a new instrument of his, which he called the " cratometer," and which was designed to measure the linear magnify- ing power of objectives ; and it would also be remembered that he (Dr. Matthews) said at the same time that he had produced an instrument, the "calliper eye- piece," by which he had been enabled to do this very simply and easily without any reference to mathematical formulae. Accurate measurement was at the root of all useful scientific research, and was especially important in observations with the microscope, and it was most desirable that every observer should append to drawings of objects the exact magnifying power employed. Their President, Dr. Beale, had set them an excellent example in this respect, never giving a figure of any object without specifying the number of diameters by which it was magnified. It was, however, no easy matter to do this. The usual method was to put the objective and object in their places, and compare the magnified image, seen by one eye, with the scale marked on a foot-rule placed at the same distance as the object, and seen at the same time with the other eye, so as to arrive at an approximation to the actual proportionate enlargement. He had himself thought it better to estimate both these measurements with one eye only, and at the same time, and he had been enabled to do this very successfully by the instrument now brought before their notice, and which was a modification of his " calliper eye-piece." He had used first of all two of Quekett's indicators together in the eye-piece, and then placed a stage micrometer instead of the object, but he found that this was not made so as to enable one of the points to be moved with sufiicient precision. He had, therefore, substituted for this arrangement one of Jackson's eye-piece micrometers, removing the glass scale, and had inserted the two points into the body of it. The points were each pro- pelled by a screw of known value, and repelled by a spring. In this instance the

60

valae of the right hand screw was exactly 50 threads to the inch, and its head was divided into 10 parts ; the left hand screw was only used for adaptation. In using this apparatus it must first be adjusted so that the points were seen in exact apposition; they must next be separated a known distance, say -['g iiiclij then place a micrometer on the stage and ascertain exactly how many of ita divisions are embraced by the points. Suppose, for instance, that the points were separated t'u inch, and that they were found to embrace 3^ inch of the micrometer scale, the proportion which these bore to each other would be obviously 3^5 in. to -,\}, le., i§^ in., or about 5| to 1, and this, multiplied by 10 — the length of the tube in inches — gave him, in the case of the objective to which he alluded, a number which agreed within one of the power assigned to it by the maker, and which he conceived to be exact. In tlie case of a f-inch objective, the points set as before mentioned, included 3^0 in., and the propor- tion of this to the 305 in., multiplied by 10, gives 100 as the power of the objec- tive. The |-in. objective gave 350 between the points at the same distance, and the proportionate number in this case was (nearly) IGJ X 10 = 165, and so in the same manner the power of any other objectives might be ascertained. The ease and facility with which this was done was remarkable, and it was so simple that it was scarcely possible to make a mistake. The value of this method also was such that the power of the eye-pieces could also be very easily ascer- tained, conversely, and another advantage was that the arrangement did not in any way detract from the value of. the apparatus as a calliper eye-piece for measuring objects in the ordinary way. There was no necessity to be confined to any special distance of the points, so that if the distance at any time were found to form a fraction, it was easy to draw out the tube sufiiciently to make it an even proportionate part, and add that quantity in the estimation.

The Chairman said that all present would be glad to receive this very in- teresting communication fi'om Dr. Matthews, and to examine the ingenious little piece of apparatus which had been brought for their inspection ; the calliper eye-piece would no doubt be remembered, and this adaptation of it would add very much indeed to its usefulness. He noticed, on looking through it, that there was a little difference between the two points

Dr. Matthews explained that he had at first met with some little difficulty as to the pointing, and the method now adopted was suggested by Mr. Hislop. A small piece of balance watch spring was broken by a blow with a hammer upon a convex surface ; the broken ends gave very sharp points, although perhaps they might only appear as such when seen in profile in one particular direction.

Mr. Ackland thought that the instrument exhibited by Dr. Matthews was certainly very ingenious, but was of opinion that all it accomplished could be done equally well without any apparatus at all. The first thing he would do would be to ascertain the apparent size of the field of view by drawing it upon paper by means of a " Beale's reflector" at a distance of 10 inches, and when this was once done accurately it would enable anyone at any Lime to ascertain the exact magnifyi g power of any objective. Suppose, for example, that the diameter of the field so ascertained measured exactly five inches by a rule. Then place a micrometer upon the stage, and read off the number of hundredths of an inch filling the field, then let this number = m diameter of field of view =^ v and magnifying power = m

then m := -— -r

m X V

61

and the magnifying power could be immediately found by a table of reciprocals, and a simple multiplication. Another plan, requiring no calculation, is to obtain an eye-piece micrometer so ruled that when placed in the eye-piece the same number of divisions fill the field of view as there are tenths of an inch in that field when drawn at 10 inches, as above described. In using this arrange- ment, multiply by 10 the number of eye-piece divisions that cover one hundredth of an inch of the stage micrometer, and the result obtained is the magnifying power. Thus, if 41 eye-piece divisions exactly cover one hundredth of the stage ' micrometer, the magnifying power would be shown to be 410. This method requires a separate scale for each eye-piece employed.

The Chairman thought that the scale was a very simple contrivance.

Mr. B. D, Jackson inquired whether Dr. Matthews used an absolute tenth of an inch, or whether he took steps to counteract the magnifying power of the eye-piece.

Dr. Matthews said that the advantage of his plan over that just proposed was that it could be applied to any eye-piece, and was not adapted merely to the one for which it, was made. The ^q in. was increased by the eye-piece, and varied with the power of the eye-piece, but he was not bound to adopt this par- ticular distance ; any other known distance would do equally well, and as the value of the right hand screw was 50 threads to the inch, and the head was divided oflfinto 10, he could adjust the points with great accuracy.

Mr. Ackland observed that inasmuch as the space employed by Dr. Matthews was a portion only of the field of view, any error which might occur would be increased in proportion to the ratio of the space between the points to that of the diameter of the field.

Mr. S. J. Mclntire said that he had for a long time adopted a plan similar to that suggested by Mr. Ackland, but had done so in what he thought was a more simple way, without the use of any tables or complex formulae. His method of procedure was as follows :— First ascertain accurately the apparent diameter of the field of the eye-piece, and reduce it to thousandths of an inch. Next place the micrometer 6n the stage and read olF the number of divisions which measure the diameter of the field, reducing them also to thousandths • then divide the number of thousandths in the apparent diameter, by the number seen on the stage micrometer, and the quotient will be the amplification re- quired.

JS.g., if the field apparently measures 5 in., and -[gg^j in, are seen on the

stage micrometer, the sum will be

5000 ^=200

or should the field be 7^ in. and ^5^0 in. be seen on the micrometer, it would be

Z^OO ^ 300

the amplification in these two cases being thus 200 and 300 diameters re- spectively.

The Chairman thought that Mr. Mclntire's plan was a very simple one, and one which could be followed by anyone.

The Secretary announced that Mr. Eichards had brought for exhibition a tube with a glass end, which was placed over the objective of his microscope for observing objects under water.

Mr. Richards said that this arrangement had been found very useful in con- nection with his erector for dissecting objects under water.

62

Dr. Dudgeon mentioned that in the " Quarterly Journal of Microscopical Science" for last July he had described a tube similar to that now exhibited ; also in " The British Medical Journal" it was referred to, and described by the Editor last month, and was highly recommended for use in examining urine or morbid secretions with high powers.

Mr. Richards explained that the tube he had with him was more especially adapted for use with low powers in connection with the erector.

The proceedings then terminated with a conversazione, at which the following objects were exhibited: —

Eye-piece Micrometer

Series of Coal Slides

Pond Life

Method of Viewing Obj ects under Water

Arachnoidiscus Ehrenbergii

Transparent Section of Injected Kidney

Gizzard of Goerius Oleus ,

Cuxhaven Deposit

Present — ^members, 63 j visitors,

...by Mr. Ackland.

Mr. Daintrey. ... Mr. Golding.

Mr. Richards. ... Mr. Tafe.

Mr. A. Topping. ... Mr. T. C. White.

Mr. Geo. Williams.

R. T. Lewis.

PLATE I. AND II.,

Illustrating W. H. Fublonge's Paper " On the Internal Structure

OF PULEX IrRITANS."

Plate I. Fig. 1. — Heticulated structure of first stomach. Fig. 2. — The gizzard. Fig. 3. — The rectal papillse. Fig. 4. — Tracheal enlargement in upper tarsal joints of the third pair

of legs. Fig. 5. — Female organs of reproduction — end view. Fig. 6. — Male ditto — A., end view ; B., lateral view. Fig. 7. — Prehensile organs and sheath plate. Fig. 8. — Lateral view of male reproductive organs, showing extrusion of

penis sheath and penis. Fig. 9. — Extremity of penis sheath — open. Fig. 10. — „ „ — closed.

Plate II. Abdominal tracheal system of the Pulex irritans.

65

On the " Illuminator Hand Microscope."

By Dr. Guy, F.R.S.

Communicated hy Mr. James How.

In submitting to the Quekett Club, at the request of Mr. James How, some account of the instrument to which I have given the name of the ^^Illuminator Hand Microscope,''' I begin by pointing out what I deem new in the parts of the instrument, and in the instrument as a whole.

There is something of novelty in the substitutioji of what may be fitly termed a Glass Lieberkuhn for a metallic one ; but it is, I believe, a quite new expedient to make the Lieberkiihn a fixed part of the microscope, and in such sort that it may be a matter of perfect indifference whether the object under examination is trans- parent or opaque.

Again, it is no new thing in my own practice to mount micros- copic objects on flat disks of crown glass, and so place them in a hand microscope that they may be viewed by any number of per- sons in succession, without possibility of disturbance. But objects so mounted on disks are new as articles offered for sale to the public.

Then, as to the instrument considered as a whole : — A hand microscope is not new in this year 1872, though I believe it to have been a novelty when I first used it for class purposes in the year 1859, now 13 years ago. And you all know that my esteemed colleague. Dr. Beale, has more recently made good use of the form of the hand, or class, microscope adapted to evening use by a lamp mounted on the same stand as the microscope itself.

A hand microscope, then, is no novelty. But a microscope that can be used in the same way, and with the same facility as an opera-glass or field-telescope, which does not require to be pulled to pieces and set up afresh each time it is used (as is the case with so many cheap microscopes), which deals exactly in the same way

JouRN. Q. M. C. No. 20. F

66 DR. GUY ON THE ILLUMINATOR HAND MICROSCOPE.

"with the 02')aqve as with the travsparent object, dispensing with the mirror and condenser, and throwing upon the opaque object so clear and brilliant a light that it c&n be seen in its true colour, form, and texture, by the common light of day, and by the light of a common candle at night ; which admits of a prompt change of a very large class of objects, and a consequent quick passage of the instrument from hand to hand in the class-room, the village school, or the social gathering — this is a novelty to which it is allowable to attach some importance.

Perhaps I shall show the use and value of the instrument best, and so give an additional interest to what would otherwise be a dry description, if I briefly narrate the circumstances that led me to adopt this new combination.

I was making a short visit to a country house of considerable pretensions, when I saw lying on the table in the drawing-room two boxes, each containing the well-known cheap microscope, with all its disjointed ,parts and teasing complications. The instruments were rarely looked at, and still more rarely put together for use ; for the functions of the several parts were not understood, the put- ting them together was a puzzle and a trouble ; and when the stem of the instrument was at length screwed into the hole in the lid, the mirror and condenser in their places, and the stage fixed, the object, if transparent, was not easily arranged, illuminated, or got into focus, and, if opaque, was still harder to deal with. On ex- amining these instruments, some small element or other of the combination was, in each case, found missing. Even when the instruments were fairly in their places, the observer was teased and tortured by the smallness of their parts, the eyes wearied by the attempt to discern objects through apertures so minute, and on a field so small, and the neck strained and fatigued by the stooping posture. The consequence of all this complication, trouble, and fatigue was, that either instrument remained for months in its box untouched ;• and, as was said by the poet Cowperof a very different matter —

" And like an infant troublesome awake, Was left to sleep for peace and quiet sake."

And yet all the while the owners of the instrument were by no means indifferent to the pleasure and instruction which a work- able microscope is so well fitted to afford ; and I became very

DR. GUY ON THE ILLUMINATOR HAND MICROSCOPE.

G7

desirous to supply them with some more useful, practical, and ornamental instrument. With this intent, I took with me, at my next- visit, the hand-microscope which Messrs. Powell and Leland had made for me some years since, leaving behind sundry fittings which I need not now describe. I had had good experience of this instrument in my class at King's College, and I now found that, even when restricted to transparent objects, it was equally useful in small social gatherings. Having some experience of the sort of pleasure afforded by the good binocular microscope brought to bear on popular objects, I found the enjoyment far greater when I substituted this hand, or class, microscope for it. The ease with which the objects mounted on the circular disks were changed, and passed from hand to hand, and the unconstrained posture, gave an altogether new character to the entertainment ; and the pleasure afforded was so great that it acted upon me as a strong inducement to find some easy means of dealing with opaque objects. I began my search with a false step. I saw, at first, no better means of throwing light upon the object than the old condenser working in a hole at the end of the instrument. The attempt was a failure, and I became more .desirous than ever of finding some expedient by which my instrument might be restored to that simplicity and readiness of use which I had always looked upon as one of its greatest recommendations when applied to transparent objects.

I accordingly put myself into communication with Mr. George Smith, foreman to Mr. How, explained the object I wished to accomplish, and the way in which I thought it might be brought about. The result of our consultations and trials was the Illumi- nator^ or Glass Lieherkiilin of which I have been speaking. It is a plano-convex lens, bored with a central aperture, and converted into a concave mirror, by silvering its convex surface. On trial, we found that an opaque object placed in the focus of the rays reflected from this mirror was brilliantly lighted, and clearly seen, in good relief, even in dull dayhght, or the flame of a common candle.

By this simple expedient, of which the effect much exceeded my expectations, my hand or class microscope was restored to that simplicity, which, as 1 have already stated, was with me one of its chief recommendations. I will not now speak of the improve- ments which may possibly be made in the shape of the Illuminator, nor of certain developments of which the instrument is obviously

F 2

Q8 DR. GUY ON THE ILLUMINATOR HAND MICROSCOPE.

susceptible. Nor will I take up the time of the Society by des- cribing the successive steps by which my employment of a disk of glass for receiving metallic sublimates (the most important advance, as it has proved to be, in the modern science of micro-chemistry), led me first to the use of a Codrington lens, then of the compound microscope, as a class-instrument, admitting of being passed from hand to hand, without displacement or disturbance of the object exhibited.

Suffice it to say that I am now in a position to state, as the result of some experience among groups of persons in society, and in school-rooms, no less than in the hands of individuals working in the closet or in the field, that we have in the Illuminator Hand Microscope a most simple, facile and effective instrument of enter- tainment, instruction and research.

Recent Observations on Diatomace^.

In the ** Lens," a quarterly Journal of Microscopy published at Chicago, U.S.A., are three consecutive papers entitled " Conspectus of the Families and Genera of the Diatomaceae," by Professor H. L. Smith, which are worthy of attention. A short critical notice of this conspectus, by Mr. F. Kitton, appears in " Grevillea" No. 4. In the first number of the " Lens," Mr. S. A. Briggs communi- cates a list of the Diatomaceae of Lake Michigan.

It has been regretted by many workers in Diatomaceae, with limited means, that the valuable memoirs published from time to time by Herr Grunow, in the transactions of foreign societies, are beyond their reach. To meet this difficulty, the Editor of " Grevillea " has commenced the publication of fac simile figures, with transla- tions of the descriptions in that Journal. The first plate of the Novara Diatoms has appeared, and the remaining two are printed ready to follow. It is proposed hereafter to publish figures and descriptions of the species in the Vienna Transactions. Additional critical observations will be made, as occasion may requii-e, by Mr. F. Kitton, the translator of the descriptions.

69

Old Nettle Stems and their Micro-Fungi. By M. C. Cooke, M.A.

As children once burnt have a wholesome dread of the fire, so children once stung have, for a time at least, a wholesome dread of the nettle. It would be some consolation to the school-boy, just smarting from the consequences of an unlucky fall into a bed of nettles, to know that alive or dead the nettle has a complete host of enemies, blighting it whilst living, and preying upon it in decay. To children of more mature age it may not be without interest to be informed of some of the foes of the nettle, which thrive at the expense of its dead and decaying stems. "We are not aware that anything of the kind has been attempted, and despite the objec- tions of those who advocate a more strictly scientific method, we will collect together a few observations on certain microscopic fungi having a common habitat, so that for this occasion the bond of union will not be one of structural relationship, but that of one common home.

It has often been objected by novices that however beautiful and instructive the minute fungi may be, they don't know where to seek them, or when found to determine their names without some con- siderable previous knowledge. There is much of truth in this, or we had not made this little experiment on the popular side of a rather dry and difficult study.

Assuming the desire on the part of the student to gain some knowledge of fungoid life, and that he has provided himself with a copy of the " Handbook " for reference as to the position, re- lationship, and technical characters of the species to be here des- cribed, little more is required save the microscope, the pocket lens, and a bed of old nettle stems in a damp situation. With these provisions a few weeks of good work is sure to follow, especially if pursued in the early spring, and with a resolute determination. It is not our intention to include any of the species which are para- sitic on the green plants, but those only that develope themselves

70

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO- FUNGI.

on the dead stems, thus limiting the period of observation to one habitat, and one time of the year. This hmitation promises far better resnlts than a more desultory method, and the experience so gained will lead thereafter to a wider field, and more extended researches.

Fig. 1.

To commence with one of the most singular of the fungi found on old net- tles, we will name Acrospermum compres- sum, because it is also one of the largest, and most prominent to the naked eye, and the most distinct that we shall have occasion to name (fig. 1). It has the appearance of little black flattened clubs, from one-and-a-half to two lines high, opening at the apex, and dis-

charging therefrom long thread-like spores. A number of these clubs are usually found together, and their size renders them rather conspicuous. The character of the spores, as well as the form of the perithecia, is so distinct, that there can be no fear of confound- ing this with any other fungus found in a similar locality. The spores are not contained in asci, or the clubs might be supposed to belong to the Sphceriacei, but hitherto no more perfect or complete condition has been observed. It is just possible that a better acquaintance may hereafter lead to the discovery of some condi- tion in which asci are produced.

Hitherto in one locality only we have found on very old and decaying nettle stems a species of Dinemasporium^ which seems to be specifically distinct from any previously described, although included in the '' Handbook" as a variety of No. 1365. This is not the place to enter upon the discussion of the limits of species in general, nor the distinctions in this particular instance, but our own opinion is strongly in favour of separating the form on nettle stems from that found on grasses. It may be observed that this fungus appears at first as rigid black bristles, bursting through the cuticle in a short linear series ; soon afterwards, especially in moist places, or during damp weather, in early spring, intense black, velvety elevations, from one to two lines in length, burst through and ap- pear on the surface. These assume an elongated cup-shape when dilated, closed when dry, surrounded by stiff, erect black bristles. The hymenium is the interior of the cup, in which is produced a

M. C. COOKE OX NETTLE STEMS AND THEIR MICRO-FUNGI. 71

great number of hyaline, sausage-shaped spores, sometimes straight, but often curved, containing one or two nuclei, and furnished at the extremity with a delicate, hair-like aj^pendage. This appen- dage to the spores is the chief feature wliich distinguishes the genus Dinemasporiiim from Excipida, and both are very mucli like hispid Pezizce with naked spores, or spores not contained in asci. Whether this is sufficient in itself to justify the maintenance of two genera is very doubtful ; in fact, so are all generic distinctions founded solely on slight differences in the character of the spores. It might be urged with equal justice that Valsa taleola should be constituted a member of a new genus distinct from that which includes Valsa leiphemia, because of the similar hyaline appen- dages to the spores of the former which are absent in the latter. Hereafter it may possibly be demonstrated that the majority of species now included under Dinemasjoorium and Excipula, as well as Solenia and Cyphella^ are conditions of Pezizoid fungi,

a The sooty black patches on old nettle stems which

^ are so common in spring are Torula herharum. This i^ is a very good example of a large genus (fig. 2), having much external resemblance to the black moulds, but structurally belonging to the Coniomycetes. The whole fructifying surface is exposed, and m this particular instance looks exceedingly like a patch of soot sjjrinkled on the rotting stems, it may be a quarter of an inch, or it may be two or three inches in length. A little of this sooty fungus examined carefully with a power equal to three hundred diameters, will reveal innumerable threads of dark sub-globose spores attached to each other in a moniliform manner, like strings of beads, but if a drop of water touches them all these spores separate from each other, without a trace of their mode of growth, and in that condition it would be exceedingly difficult to determine the genus or order to which the fungus belongs.

Another fungus belonging to the same order, and with a similar structure, has also been found on nettle stems in the month of October. This is Septonema elongatispora. The threads in this instance also consist of spores attached end to end as in Torula^ but, instead of being simple, the spores are cylindrical, with one or two septa, and quite colourless. The tufts are effused over the stems, giving them a whitish mouldy appearance, very different to the sooty patches of Torula, and more like those of Dendryphium griseum.

72 M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI.

Altliongli this and some other species here enumerated have only- been detected on nettle stems, it does not follow by any means that they are confined to such a habitat, or that some other allied species found on other herbaceous plants may not also occur on nettle stems. At present our knowledge of the distribution of these minute forms is too limited for generalizations of this kind.

Externally, and to the naked eye, resembling a very thin patch of the Torvla, another, and widely different fungus, may be found in a similar location. In this instance the coating is so thin that it only gives a greyish appearance to the stems, the black threads being sprinkled about in patches two or three inches in length. When held up between the eye and the light, and examined by a pocket lens, the twig appears velvety with erect black hairs, an appearance never presented by the dense growth of the pulverulent Torula. This is the general appearance of two species of Den- dryphium^ a genus of black moulds distinguished by the jointed threads being branched in the upper portion, bearing at their apices septate spores, which are often attached end to end in a series. In one species^ the fertile branches are radiating, or form a dense head, and the septate spores are variable, with the joints quadrate. This is called Dendryi^hium comosvm. In the other species, Dendryphkim cuitiim, the branches are shorter, and forked ; the spores are curved, with from three to seven septa, constricted at the joints. The shorter forked ramuli, and the much constricted articulations of the spores, are characteristic of this species. Both of them are found on old nettle stems, as also a third species — Dendryphium griseum — which is very different in its appearance to the naked eye. In this latter the stems are covered in patches of some extent, with a bluish-grey bloom, something like the bloom of a ripe plum. The threads are but slightly branched, and the spores are cylindrical, with a little point at each end, and arranged in chains ; they are at length uniseptate, and colourless. There is something so very dif- ferent in the appearance of this species and its colour, that at first it would scarcely be recognized as belonging to the same genus as the two preceding. It is often very common amongst the debris of an old bed of nettles.

Another black mould may be named in this association, which, though perhaps much less common, is even more beautiful (fig. 3). It is Arthrohotryinn atrum. In this instance the common stem is composed of jointed threads, which are attached together

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI.

73

■!)

Fisr. 3.

side by side, and expand at the apex into a head or tuft of large, somewhat elliptic spores. These spores are divided unequally by transverse septa, the central portion being coloured brown, and the ex- tremities colourless. By a little careful manipulation this mould may be examined in situ, although when such a high power as a third or a quarter-inch objective is required for an opaque object patience and perseverance are requisite. We have found that a third with a small nozzle, bevelled at the edge, on the conti- nental rather than the English method of mounting the lenses, is the most effective. Such an objective admits of more light being thrown down upon the mould by means of a bull's eye and side reflectors than can be accomplished with the usual English objectives. With- out intending any invidious allusion to one maker rather than another, we may be permitted to state that such an objective was made for us on the abcve plan by Mr. Swift, at a moderate price, and has succeeded better than any other plan we have adopted to secure the examination of such opaque objects as moulds, and other microscopic fungi, in their natural condition, by means of high powers. Doubtless the lime light recommended by Mr. Green for the examination of diatoms would be a valuable adjunct, although we cannot as yet speak from experience. It cannot be urged too often or too strongly that, in order to see objects as they really are, they should be viewed by the opaque method, and not by having the light thrown through them. To confide in such a mode as the latter may save trouble, but it is only a delusion and a snare. Another black mould found by Mr. Broome, on the old stems of tlie nettle, is Acrothecium simplex. In this genus the jointed threads are either simple or branched, with the spores clus- tered at the apex (fig. 4). In the present species the threads are simple and flexuous, bearing a few almost clavate spores at the apex. The threads are brown, and the spores slightly coloured, divided transversely by four or five septa. Mr. Broome found this species in the month of De- cember, and as there is no other record of it, pro-

74 M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI.

bablj it is rather uncommon. The tufts of spores at the ai:)ex of the simple dark brown threads are sufficient to distinguish it readily when met with. Like its congeners it appears in thin velvety patches on the stems, and is scarcely visible to the naked eye, ex- cept in the darker tint of the patches.

There is a very pretty and interesting group of fungi which are well represented on old nettle stems, possessing a high organization, and, when fresh, often beautiful. These belong to the genus Peziza. It may be premised that the substance of these fungi is between fleshy and waxy, that they are more or less cup-shaped, either smooth or hairy externally, sometimes sessile and sometimes stalked, and that the sporidia are contained in asci embedded in the substance of the cup. The method employed for their examination and preservation, with some particulars of their structure, will be found in a previous communication on '' Nucleated Sporidia " (vol. ii., p. 251).

It is one of the " commonest objects " to see old stems of nettle sprinkled from the base upwards with orange points about the size of pin's heads. When the weather is damp these little points are very prominent, swollen, and gelatinous, crushing readily under the finger like jelly, and of a bright orange colour, giving a distinct colour to the stem, so that even at a distance the orange tint may be recognized. This tremelloid orange fungus is the precursor of a species of Peziza of the same colour, consistence, size, and general appearance, of which it isjiow regarded as the conidiiferous condi- tion. If one of the orange pustules, whilst moist and tremelloid, be subjected to examination, it will be found to consist ot delicate branched threads, immersed in the gelatin, and bearing on their tips, at the surface of the masses, a great number of minute colour- less spermatia or conidia. This was formerly named Fusarium tremelloides, and was for a long time included amongst the tremel- loid fungi as a Dacrymyces. In this condition there are no traces of asci. At a later period, and what would at first seem to be the same fungus, so identical in habit, size, and colour, makes it appear- ance. The only distinction between them which even a pocket lens will reveal, is that of a depression in the centre of the pustules, which have now assumed a cup-shape. Crushed in a drop of water under the microscope, the branched threads are no longer to be seen, but instead thereof transparent elongated sacs, or asci, each containing eight small sporidia. This is Peziza fusai ioides. On

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI. i 0

referring to the " Handbook," it will be observed that this Peziza belongs to the section Mollisia, in which the cups are sessile, ex- ternally naked, and of a soft texture. We recently received a closely allied species on Aster stems from the United States, which was figured and described in " Grevillea " (No. 1, p. 6, fig. 6) as Peziza assimilis. In both these, and in some few others which continental authors have associated together under the generic name Calloria^ the substance is much more gelatinous than in the majority of the species of Peziza.

Two or three species of Peziza. found on these stems are charac- terized by being hairy externally, and hence they belong to the section Dasyscypha. The most common of these is a very pretty little white fungus, covered outside with rather long white hairs. The cups are sessile and minute, seldom open, except in quite wet weather, and even then only partially so. But the most unsatis- factory point in their history is that they always appear to be barren. No author gives any account of the fruit of Peziza villosa^ and yet all agree in retaining it as a species of Peziza, whereas the strong presumption is in favour of its being a Cypliella, and unless a perfect hymenium with asci and sporidia can be found it has no title to be regarded any longer as a Peziza. Here is one point which may be investigated and settled by any student who takes advantage of this communication to commence the study of micro- scopic fungi.

Allied to this, but apparently much less common, is a woolly, white Peziza, first discovered in Scotland by the late Dr. Greville, and called by him Peziza piano 'Umhilicata. It is gregarious in its habit, small and sessile, wholly white, becoming expanded, and quite flat, with a little dimple in the centre. The hairs around the margin of the cup are very regular, forming a delicate fringe. As it grows old, it assumes a yellowish tint. Although in many points this closely resembles the preceding, it will not be a difficult matter to distinguish the one from the other, since this soon becomes ex- panded, and has asci and sporidia, so that it is a true Peziza. A common white- stalked Peziza, with a woolly exterior, may sometimes be found on nettle stems, but must not be confounded with this. It is Peziza virginea, and grows freely on all twigs that are covered over with dead leaves, in damp spots.

Another species belonging to the same section is Peziza sul- phurea: This is also sessile, but much larger than the jjreceding ;

76 M. C. COOKE ON NETTLE STEMS AND- THEIR MICRO-FUNGI.

sulpliur-coloiired, and woolly externally, approaching to brown, especially when dry, with the disc or inner surface of the cup of a pallid hue. This is a very pretty object, but the colour varies con- siderably in its depth and brightness. The asci contain eight fusi- form sporidia, which seem to be sometimes divided transversely by three septa, but probably this may only be a division of the endo- chrome. It is very difficult at times to make out distinctly the form of the sporidia when still contained in the asci, or the septa when free, if the membrane is very delicate. To assist in this a drop of tincture of iodine should be run in under the covering glass whilst the asci are being examined. The membrane is tinged of a brownish colour by this means, and is often rendered quite distinct.

The remaining species of Peziza found on old nettles belong to the section Hymenoscypha, in which the cups are stipitate, and somewhat membranaceous, and though smooth internally the margin is often toothed or fringed. The Peziza infiexa of Bolton is a pretty species, of a dirty yellowish white, with the margin of the cup beset with regu^_ar triangular teeth. It is figured by Bolton in his " Funguses of Halifax " (plate 106, fig. 2). The marginal teeth are not erect, but bent inwards towards the centre of the cup.

Closely allied to the preceding is Peziza coronata^ of a nearly equal size, similar in colour and in length of stem, but differing in the margin being beset with a fringe of bristly hairs, instead of the distinct, inflexed, triangular teeth of the previous species. The alliance of these is so intimate that some authors have not hesi- tated to regard them as forms of the same species, whilst others maintain that their differences, though minute, are permanent.

A yellow, or brownish yellow Peziza^ is found on stems of the nettle in Northern Europe, which, from the campanulate form of the cups, has been called Peziza campanula (Nees.), but it has not been recorded in Britain. The sporidia in this species are slender, and with from three to five transverse septa. It is found in August and September.

A much more distinct, but by no means common, species is Peziza striata, with the cup turbinate, or top-shaped, of a brownish colour, striate externally, and with a short pallid stem. The mar- gin is always disposed to close inwards, but is not fringed or toothed. The inner surface of the cup is pallid. The sporidia are fusiform, and without any indication of septa. It is so much addicted to

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI. 77

making its appearance on stems of nettles that Persoon described it under the name of Peziza urticce. When fresh there is a pruinose, or frosted character about the margin of the cup.

It is quite probable that other species besides those now enu- merated may be found growing on such a good-natured host as old nettles -seem to be. Of later years a number of species of the old genus Peziza have been removed and constituted a new genus, under the name of Helotimn, chiefly on account of the disc being always open, and often convex, as well as some minor distinctions. One species of Helotium occurs on nettle stems, as well as some other herbaceous plants ; it is Helotium herharum. The smooth waxy cups are whitish with a tinge of ochre, and flattened, or a little convex ; the stem is very short, so as not to raise the margin of the cup above the surface of the stems. The sporidia are long and narrow, blunt at the ends, sometimes straight, and sometimes curved, with occasional indications of three transverse septa, which may possibly be spurious.

There are to be found on the same old nettle stems a group of fungi, partaking of such general features in common that we may call them the Xettle Spha?rias. The distinguishing mark of this group is that the sporidia are contained in asci, which are enclosed in a more or less carbonaceous peritheciiim. Reducing this de- scription to more common-place language, it may be said that the whole fungus consists of a blackish receptacle, somewhat like a "water-bottle in shape, with a nearly globose body and rather short neck. This bottle is sometimes imbedded and sometimes exposed ; sometimes single and sometimes in groups or clusters, or even in confluent masses. The interior of these little bodies contains something very like a minute drop of gelatine composed of long naiTow bags of transparent membrane called asci, each of which encloses, when mature, about eight smaller bodies of the nature of seeds, termed sporidia. Mixed with the asci are long, slender, hair-like, colourless filaments, considered by some as abortive asci, but which are termed paraphyses. Such are the Spha?rias. There are several species of them found on old nettle stems, and the most important of them will be briefly noticed. First, and commonest, is the gregarious species found near the bottom of almost e\rery old nettle stem that is plucked up. Shining black conical flasks, with a flattened base, collected together by scores, throw off the cuticle and become exposed as they approach maturity. Examined

78 M. C. COOKE ON NETTLE STEMS AND THETR MICRO-FUNGI.

closely by means of a two-iiicli objective, these bottle-shaped bodies will be detected having two forms, one conoidal with a short neck, and one flattened with* a longer acute neck. These are two forms of the same fungus. The former contains the asci and sporidia, the latter free bodies, much more numerous and minute, which are spermatia. There is still some confusion in the names which are applied to these two forms. It is generally admitted that the acute form, containing spermatia, is the Sphceria acuta of Hoffman, but not a complete or perfect Sphjeria, and hence called by Berkeley Aposphceria acuta. The other form, which contains the asci, is re- garded as the perfect condition of the same fungus, and some authors apply to it the name of Sphceria acwto, whilst others regard it as the Sphceria coniformis of Fries, and apply to it that name. Whichever name is adopted, all seem at least to be agreed that the two forms represent the spermogones and ascophores of one and the same fungus. If the flattened form with the acute neck be examined, by crushing one of the perithecia in a drop of water, its interior will be found filled with a mass of very minute, linear, curved bodies, at first attached to delicate pedicels, and these, produced from the inner wall of the perithecia, are the spermatia. It is pro- bable that they have some function to perform in relation to the fecundation of the sporidia in the other form. The more conoidal, and rather larger perithecia, contain asci, each enclosing eight transparent fusiform sporidia, which, when mature, are divided transversely by numerous septa, and acquire a yellowish tint.

Some two or three years since Dr. Capron, of Shere, first called our attention to a Sphceria found by him on old nettle stems, in which the perithecia were far less numerous, more imbedded, and usually covered, except the broad gaping mouth, by the cuticle of the stem. In this instance the sporidia are as long as the ascus in which they are contained, and lie side by side in a bundle, without crossing or interlacing each other. These sporidia are threadlike, and divided by transverse septa into a great number of cells, about equal in length to their breadth, and of a yellowish tint. From examination and comparison we became satisfied at the time that this was the species named by Dr. Eabenhorst Sphceria urtica?, but hitherto have only seen it from Shere. This has many points of resemblance to Spharia rnhella, which is also very occasionally found on nettle stems, but there are no red spots, and there is none of the pubescence on the perithecia.

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI. 79

Another, and still more singular Sphceria was also found by Dr. Capron on nettle stems at Shere, in wliich the sporidia are different from any other that we have ever seen. The perithecia are de- pressed and covered by the cuticle, so that only the mouth is visible.

Fig. 5. In wet weather the perithecia can be readily seen through the cuticle, but when the stems are dry it is almost hopeless to search for this species. The sporidia are also as long as the ascus in which they are contained, crossing each other near the apex, but when free are found to be twice or thrice septate, bent at the constric- tions, and again spuriously septate two, or three, or more times in every joint (fig. 5). From the peculiarly angular manner in which the sporidia are bent when free, this species was named Sphceria ulnas- j)ora. By comparison with the fruit of Sphceria acuminata, com- mon on thistle stems-, and the Sphceria urticce and Sphceria rubella named above, this will be found markedly distinct from all. It may be noted that whilst in most instances Sphwria acuta will be found at the base of the stems, Sphcerice urticce and Sphceria ulnaspora occur higher up, usually about midway of the stem.

SphcBria doliolum is by no means an uncommon species on the stems of umbelliferous plants, and sometimes on old nettles. The perithecia are of a shining black, and concentrically channelled, so that a ridge seems to run round the perithecium, giving it a very distinct character. Sometimes the perithecia are very conical, as in a variety described by Mr. F. Currey as Spha^ria Helence. The sporidia are arranged in two rows in the asci, and are yellowish, almost fusiform in shape, and divided by from three to five septa, with constrictions at each joint. Spermogones are often found mixed with the perfect perithecia, and these contain a great number of minute colourless spermatia. The second joint of the sporidia is sometimes swollen so as to be broader than the rest.

The stems of nettles are often sprinkled so densely with the small black perithecia which nestle beneath the cuticle, as to have a grey, nebulous appearance, which are probably the Sphceria nehulosa of old authors, or partly so. These very minute perithecia do not con-

80 M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI.

tain asci, but innumerable minute bodies of the nature of spermatia, and the perithecia are therefore the spermogones of some Sphceiia, and in some instances of Sphceria svjoerjlua, which is occasionally mixed with, or in close proximity to the spermogones. In this species the perithecia are small and delicate, although twice as large as the spermogonia with which they are as.^ociated, and always covered with the cuticle. The sporidia are oblong and colourless, in two rows, and divided across the centre by a septum into two equal cells. The spermogones seem to be, in part at least, the Phoma nebulosum of authors.

A group of the old genus Sphceria is characterized by the broad orifice of the perithecium, which is flattened laterally, so as to bear some resemblance to a mouth with two lips. These perithecia are usually imbedded in the matrix, so that the mouth only is exposed. Recently this group.has been regarded as a distinct genus, from the form of the mouth principally, under the name of Lophio stoma, although some authors still hesitate to accept it as a good generic distinction. Two of the members of this group are found on nettle stems ; one having been first detected by Dr. Capron, of Shere, a few years since, and described under the name of Lophiostoma sex- nucleata. It appears to succeed SphcBria acuta, and is often over- looked, from its casual resemblance to the remains of the dispersing perithecia of that species. The old stems on which this species is found are so far advanced in decay that they are usually tender and friable. The sporidia are fusiform, slightlv curved, and five-septate, with a constriction in the centre, each articulation contains a single nucleus, from which the name of the species is derived.

The other species is Lophiostoma canlium, which is very similar in external appearance, but differing in fruit. The sporidia are also fusiform, and attenuated towards each extremity, often curved, with a greenish tint, and divided transversely by seven septa, exceeding by about one-sixth or one- eighth the length of the sporidia in Lophiostoma sex-nucleata. The same species is also found on the stems of Epilohium hirsutum, and other herbaceous plants.

There is a very interesting group of Sphc^riacei, in which the perithecia are of a softer and more waxy substance, usually brightly coloured, of which a new species has recently been described by Nylander, under the name of Nectria dacrymycella, which is found in Northern Eaiope on old nettle stems. The perithecia are orange-

M. C. COOKE ON NETTLE STEMS AND THEIR MICRO-FUNGI. 81

yellow and minute ; the sporidia fusiform, and delicately unisep- tate. It has not hitherto been met with in Britain.

This enumeration inchides the majority of the species of micro- fungi which have as yet been detected on the stems of old nettles in Britain. Formidable as the list may appear, there are two or three others which have been found on the Continent, and which, by dint of perseverance, may still be found in this country. At any rate, we have made good the assertion with which we com- menced, that the nettle has a complete host of enemies, blighting it whilst living, and preying npon it in decay. In illustration of the enemies which are parasitic upon it whilst living, we have been unable to devote space equal to that already occupied, leaving out of the calculation all the insect enemies for the entomologist to discuss ; but the moulds, cluster-cups, Septoria^ and other para- sites of living nettles, are scarcely less numerous than those which flourish on its decay.

The following is a list of the species of micro-fungi alluded to in this communication : —

Acrospermum compressum. Tode. Dinemasporium var. herbarum. Toriila herbarum. Link. Septonema elc«igatispora. Preuss. Dendryphium comosum. Wo2l. Dendryphium curtum. B. S; Br. Dendryphium griseum. B. ^ Br. Arthrobotryum atrum. B. <^ Br. Acrothecium simplex. BerJc. Peziza fusarioides. BerTc. Peziza viliosa. Pers. Peziza plano-umbilicata. Grev. Peziza sulphurea. Pers. Peziza inflexa. Bolt. Peziza coronata. Bull. Peziza campanula. Nees. Peziza striata. Fr. Helotium herbarum. Fr. Sphasria acuta. Hoffm. Sphaeria urticae. Rahh. Sph^eria ulnaspora. Cooke. ' Sphjeria rubella. Pers. Sphaeria doliolum. Pers. Sphseria superflua. Awd. Lophiostoma sex-nucleata. Cooke. Lophiostoma caulium. Fr. Nectria dacrymycella. Ngl.

JoURN. Q. M. 0. No. 20. G

82

Notes on the " Black Knot." By C. H. Peck, Esq., of Albany, New York.

What is black knot ? To tliis question Dr. Fitch, Entomologist of the New York State Agricultural Society, answers : " It is a large irregular black wart-like excrescence which grows upon the limbs of plum and cherry trees, causing the death of all the branch above it and extending down the limb farther and farther every year till the whole branch is destroyed, other limbs at the same time becoming affected in the same manner, and also the limbs of other trees in the vicinity. If it is neglected, it in a few years kills the tree."

The late lamented B. D. Walsh, Entomologist of the State of Illinois, thus defines it : " It is a black, puffy, irregular swelling on the twigs and smaller limbs of plum and cherry trees, and in one instance that came under my observation, of peach trees, mak- ing its first appearance in the latitude of New York early in June, and attaining its full growth by the end of July. Usually a tree that is attached in this manner is affected worse and worse every year until it is finally killed, and where one tree of a group is af- fected, the malady usually spreads to them all in process of time."

According to our own observations the death of the branch above the excrescence is not always produced by the first attack. In such cases the malady extends ujDwards as well as downwards. The time of the first appearance of the excrescence is in late autumn, although the external development of the fungus is not manifest until the following May. We have never found it on peach trees.

Let us now see what is written concerning the origin of black knot. Schweinitz, the botanist who wrote the original description of Sphceria morbosa, the fungus that develops itself on the ex- crescence, seems to have been in some doubt concerning the origin of the tumour. In his description he uses these words : " Hcec massa num sit effectus ictuum Cynipis nescimiis, videmus tamen hic

C. H. PECK ON THE " BLACK KXOT." 83

iUic exesvm foramen, forte e frofvndo progressa^y At a later day, in writing n})on this same subject in Lis SynojDsis of North American Fungi, he says : " Pavcis cinnis post, fere omnes clesfrvQti sunt, comhinato furore hvjvs fmigi et Ct/nifisy And again he says : " JEt in Jus omnibus Cynipis fungnsqve incepiunt scevire^ Thus he constantly associates the insect which he calls Cynips with the fungus, without definitely assigning the honour or dishonour of the mischief to either. We find the following in Harris''s Treatise on Injurious Insects : " The plum, still more than the cherry tree, is subject to a disease of the small limbs, that shows itself in the form of large, irregular warts of a black colour. Professor Peck referred tbis disease, as well as that of the cherry tree, to the agency of insects. Dr. Burnet rejected the idea of the insect origin of this disease, which he considered as a kind of fungus. * * * But whether caused by vitiated sap, as Dr. Burnet sup- posed, or by the irritating punctures of insects, which is the pre- yailing opinion, they form an appropriate bed for the growth of numerous little parasitical plants or fungi."

Dr. Fitch claims to have made a careful investigation of this subject, and as his observations are quite accurate we again quote from his address : " There has been much speculation as to the cause and true nature of these excrescences. * * Most persons suppose them to be of insect origin. The larvee of the curculio are almost always found in them, and these larvae consume nearly all the spongy matter of the warts, but do not touch the little fungus growing on their surface, which remains, forming a kind of shell, after the whole inside is devoured. But as these excrescences are sometimes found wholly free from curculio larvae and all other worms, it is obvious they are not the cause of their growth. * * Suffice it to say that now, having carefully examined these excre- scences from their commencement onward through their subsequent growth, I am prepared to say, with the fullest confidence, that the microscope shows nothing whatever about them, externally or in- ternally, indicating that an insect has anything to do with causing them." Then, after giving his views as to what constitutes a fun- gus, he says : " We arrive at the conclusion that these excrescences are not of insect origin, and are not a vegetable fungus, but are properly a disease of these trees, in many respects analagous to the cancer in the human body."

Mr. Walsh, whose definition of black knot we have already

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84 C. H. PECK ON THE

quoted, agrees with Dr. Fitcli in concluding that the excrescences are not of insect origin. He also claims to have carefully watched the black knot through all its stages from its earliest commence- ment to its complete maturity. He affirms that he bred from the galls five distinct species of insects beside the curculio, but that not one of these could be considered a true gall maker. He, there- lore, very justly concludes that the excrescences are not of insect origin, but of fungoid origin ; and this conclusion, we may add, is entirely in accordance with our own view of this subject. Our reasons for adopting this view are briefly these : —

1st. The excrescence itself is similar in structure to other ex- crescences which are known to be of fungoid origin, and at the same time it is quite dissimilar to most insect galls produced in twigs and young branches.

2nd. The time of its development is opposed to the probability of its insect origin. We are well aware that our knowledge of in- sect galls is extremely limited, and that here we are treading on dangerous ground and may hereafter be obliged in our turn to apologise to the entomologists, but so far as our observations ex- tend, insect galls are developed in the warmer seasons of the year, i. <?., in spring, summer, and possibly early autumn. Those that continue to be the domicile of the young insect during the winter are, so far as we have observed, fully grown in autumn, and do not increase in size the following spring, a character which does not hold good in the case of black knot.

3rd. The furgus is always present with the excrescence, and its mycelium may be detected even in the earliest manifestation of the tumour, and this fungus is never found apart from the black knot. To our minds this alone is a sufficient argument for our belief in the fungoid origin of the excrescence. Who ever heard of any undoubted insect gall being always accompanied and inhabited by a fungus? On the other hand, the larvae of insects are not always present in the excrescence, and of those insects that have been bred from it, none, we are told, have been true gall makers.

Like others from whose writings we have quoted, we also claim to have examined the black knot carefully in its various stages of development, not entomologically it is true, but botanically, from which it is not unreasonable to suppose that we may have observed some details in its development which escaped their notice. We desire, therefore, to express the results of our own observations,

C. H. PECK OX THE *' BLACK KNOT. bO

because in one or two points vre cannot quite agree with the in- ferences and conchisions of former investigators.

If the smaller branches of a cherry tree that is suffering from an attack of black knot be carefully examined in Xovember, some of them will be found to be slightly swollen for a little distance immediately below the excrescences. The cuticle of the bark will be cracked open here and there, revealing the soft tissues of the inner bark. If a minute portion of this inner bark be examined by the aid of the microscope, slender jointed filaments or threads may be seen, that have insinuated themselves among the bark cells. These threads are the primary vegetating condition of the fungus, and are known to botanists as wycelium. During the winter the en- largement of the branch remains nearly or quite stationary, but with the advent of spring and the renewal of vegetable activity, the tumours increase in size, the chinks in the bark become wider and more numerous, and by the end of May small, dark, green stains are visible in the crevices of the bark. These greenish patches gradually increase in size until in some instances they com- pletely cover the whole surface of the excrescence with a soft, velvet-like coat. Such specimens were once sent to me from the west, where they had been pronounced by a scientific journal to be a new species of black knot. A microscopic examination of this greenish coating reveals the fact that it is composed of innumerable upright, jointed, flexuous threads or flocci, which bear upon their summit oval or oblong spore- like bodies, at first simple, but soon becoming one or more septate. This is the first external develop- ment of the fungus, and in the systematic classification adopted by botanists it belongs to the genus Cladosporium. This genus, however, we apprehend is destined to be overthrown, its species being only an early form of development of species of Sphceria. Indeed those celebrated European mycologists, Tulasne and Cooke, already deem the very common Cladosporium herharum to be only a condition of Sphceria herbarum. And here we have another quite clear case of a similar dimorphism, for I never yet have seen a young black knot excrescence of the cherry tree in spring on which I could not detect the Cladosporium. In a few weeks this Cladosporium growth is succeeded by numerous minute, black, globular bodies, scarcely as large as the head of a small pin. These usually cover the whole surface of the excrescence, and are often BO closely crowded together that they partially lose their globose

86 C. H. PECK ON THE " BLACK KNOT."

form. This stage of the fungns development has evidently been mistaken by some for its complete deveL'pment. In the work of Harris, on Injurious Insects, we find the following statement in re- ference to this fungus; "they come to their growth, discharge their volatile seed, and die in the course of a single summer." And in the Practical Entomologist for March, 1866, we find this statement : *' Towards the middle of August, the new black knot, having perfected its seed, gradually dries up, and becomes intern- ally of a reddish-brown colour. In other words, like so many other annual plants, it dies shortly after it has perfected its seed." Again, in the March number for 1867, Mr. Walsh says : " I showed that black knot is nothing but an assemblage of minute funguses, which perfect their seed, or ' spores,' as botanists term it, the latter end of July ; and that consequently, as this fungus is an annual plant, by cutting off and destroying the black knot early in July, its further propagation may be effectually stopped."

Now, according to all of our observations the seed of the fungus is not perfected in July and August, nor indeed until some months later.^ Externally, it is true, the fungus appears to have attained its full develo])ment, but if one of these little black globes —j^^rz- thecia they are called by botanists — be taken from the tree at this time and crushed on the slide of the microscope, and its contents examined, little oblong, pale membranous sacs will be seen. They are not all equally developed, and are evidently rudimentary. If we again examine the contents of some of the perithecia, collected at a later period, say in November, we shall find that our rudimen- tary sacs have increased considerably in size. They are now cylin- drical, and contain a greenish, grumous endochrome, from which the spores are destined to be formed. The earliest period in which we have found the spores developed isthe middle of January. In specimens collected January 13th, spores were found in a few of the sacs, but most of them were yet filled with their greenish contents. We have found spores in specimens collected as late as June, there- fore the time in which the fungus perfects its seed may be said to be from January to June. Thus it will be seen that the plant is not an annual, as some have affirmed, but one that requires from fourteen to twenty months from the time of its first manifestation as an incipient excrescence to the time of the maturity of its seed ; and from eight to fourteen months from the time of its first ex- ternal appearance as a plant to the perfection of its seed.

C. H. PECK ON THE " BLACK KNOT." 87

Having thus dwelt at some length on this subject, we will briefly notice one or two inferences, which we find in the articles of the Practical Entomologist, from which we have quoted. We would not even notice these did we not believe them erroneous and fraught with mischief. It is stated that " about the last of July or the first week in August, there grows from each fungus on the surface of the black knot a little cylindrical filament about one-eighth of an inch long, which no doubt bears the seed or spores, as they are technically termed, of the fungus, and that these filaments very shortly afterwards fall off and disappear, leaving behind them the hemispherical plates, which alone had been hitherto noticed by botanists. * * I discovered that the filaments not only cover the entire surface of the black knot itself, except where a few