Z << JO ALIS na Digitized by the Internet Archive in 2008 with funding from Microsoft Corporation http://www.archive.org/details/eveningsatmicrosOOgossuoft * ‘ f i! ‘ é \ , I i « 1 ‘ 1 » rE C is e . ' ae 4 on > 4 > “4° . : al ' RE ae ui | - : \ EVENINGS At THE MICROSCOPE EVENINGS me TE, MICROSCOPE; OR, RESEARCHES AMONG THE MINUTER ORGANS AND FORMS OF ANIMAL LIFE. BY PHILIP HENRY GOSSE, F.R.S. NEW YORK: D. APPLETON AND OOMPANY, 1889. mt ort a uP ath i eo u ae ha) os : : ‘ a ’ -— F : BELT " a : hy : 2 i us Taos ¥% f Ae os kita +o / Vv ; ‘\ v4 ~ . uy - — PREFACE. To open the path to the myriad wonders of creation, which, altogether unseen by the unassisted eye, are made cognisable to sight by the aid of the Microscope, is the aim and scope of this volume. Great and gorgeous as is the display of Divine power and wisdom in the things that are seen of all, it may safely be affirmed that a far more extensive prospect of these glories lay unheeded and unknown till the optician’s art revealed it. Like the work of some mighty genie of Oriental fable, the brazen tube is the key that un- locks a world of wonder and beauty before invisible, which one who has once gazed upon it can never for- get, and never cease to admire. | This volume contains but a gleaning: the author has swept rapidly across the vast field of marvels, snatching up a gem here and there, and culling one and another of the brilliant blossoms of this flowery vi PREFACE. region, to weave a specimen chaplet, a sample coronal, which may tell of the good things behind. Yet the se- lection has been so made as to leave untouched no con- siderable area of the great field of Zoology which is under the control of the Microscope; so that the stu- dent who shall have verified for himself the observa- tions here detailed, will be no longer a tyro in micro- scopic science, and will be well prepared to extend his independent researches, without any other limit than that which the finite, though vast, sphere of study itself presents to him. The staple of the work now offered to the public consists of original observation. The author is far from thinking lightly of the labours of others in this ample field; but, still, it is true that, respecting very many of the subjects that came under his notice, he found, in endeavouring to reproduce and verify pub- lished statements, so much perplexity and difficulty, that he was thrown back upon himself and nature, compelled to observe de novo, and to set down simply what he himself could see. The ever accumulating stock of observed and recorded facts is the common property of science; and the author has not serupled to reproduce, to amplify, or to abridge his own obser- vations which have already appeared in his published works and scientific memoirs, as freely as he would have cited those of any other observer, in which he had confidence, and which were germane to his pur PREFACE. vu pose Yet in almost all cases the observations so used have been subjected to renewed scrutiny, and have been verified afresh, or corrected where found defective. In order to. relieve as much as possible the dryness of technical description, a colloquial and familiar style has been given to the work; which has been thrown into the form of a series of imaginary conversaziones, or — microscopical soirées, in which the author is supposed “to act as the provider of scientific entertainment and instruction to a circle of friends. It is proper to add, however, that the precision essential to science has never been consciously sacrificed. A master may be easy and familiar without being loose or vague. A considerable amount of information will be found incidentally scattered throughout the work, on micro- scopic manipulation—the selecting, securing, and pre- paring objects for examination ;—an neue matter, and one which presents a good deal of practical diffi- culty to the beginner. Not a little help will be afforded to him, also, on the power to observe and to discriminate what he has under his eye. In almost every instance, the objects selected for illustration are common things, such as any one placed in tolerably favourable circum- stances, with access to sea-shore and country-side, may reasonably expect to meet with in a twelvemonth’s round of research. “il PREFACE. The pictorial illustrations are almost co-extensive with the descriptions ; they are one hundred and thir- teen in number; all, with the exception of eighteen, productions of the author’s own pencil, the great ma- jority having been drawn on the wood direct from the Microscope, at the same time as the respective descrip- tions were written. He ventures to hope that they will be found accurate delineations of the objects repre- sented.* Torquay, February, 1859. * The subjects on pp. 48, 54, 112, 114 (the lower figures), and 175, have been copied, under the courteous permission of the publisher, from Yr. Carpenter’s valuable work, ‘The Microscope, and its Revelations.” ( Shurchill, London.) LIST OF ILLUSTRATIONS. WEIOUTSE OEE QUSEiaos Ccciccios cc esive rece os oaeisrecesn oe cesses oes aumento ceuet os sonnenee PEO Rg SOMATA FVAT OF MOUSE scescsccedoas ose /saccecscowcneccescdecuzoseoene VATION OBB AT a acctcsancsiccc eseses cnc cscs, « iodecsessecuewes oes soeesectleseeneeenes FATRWORMUNDIAN *DAT 2 scccsccasscssocseaesseduvieesscccecls Daedwe das selects smears POR SHATR OF! DERMESTESS 5. xsscccscssocecetesccesdcsceses sda geleuesatesdees IDARESOR) CLOTHING PEATHER. OF HOW. .isccccccesesscs scccctotesdecde sense ae HEAD OF CHEESE-MITE .........-.esceceess saceccesteceicoeecere teeeae eee A IBRACHIONUS) soc sostsceccsedces cera wee eeee sadlicele hres tee i eoseekece eases MovuTH OF BRACHIONUS ........cccccceccesccese Onaccaence sovesdsccececOeteneee 5 WURTPTATE 820252 os eee esl secede eee oreeeen asstovecseres BPE PEE Sey onic See SKELETON WHEEL-BEARER.........c+sccecccees Se decendecat so tae can Cee os LIST OF ILLUSTRATIONS. TTR BoE pnp Pen OCC OBEDUD DIG HOSBOS US DOE ROSBUGO eco saaqaDDOdoo00cH, Saosecad MCODMW HERE DRAB ss vcrcsecesistele sicccesssssiccscecescpesesciseasel ss tosatee’ MimGulere PRD) ChORE-VWiHEET cccccieesesseosesceseccsssccessasoncasenccscssucncsans WAYS) ORG UL UBE- WHET. cancccscicccccrccsiese cncscesciiscscesiessocesscncscsseiss ROO TBO AUS see cacienecenicccccbl ccisccsecvccsccccesesiectcucechoacidvencwcsiclesaclisiaee TTROATI OR WL HEGH: LATD) ORE Neccccceccsceccscesssecercccvccseciccssccnecsersse PIO RRS OOEescce ccs ceaniccccecssnacedes tecossoscicoesceicsiecciasee/rsvislsslslalsiesteise's)sies PUSHING-POLES OF SERPULA vsccccscccecccccccccccccccccccsccccccesccorecsscnce EIGQOKAIOMM ERP UMAT esos es sscccscccsesccsicsesisisccccecccescesceecacceccccesosiaselesie BUN SM ORM GELEN US satis ce ra ceniesiecices eee occesecnlasels'selocicclslecllelcisiscisisiecieeleiesie sic FIBAD OF PEDICELLARIA.......sesccscccccccocccccccccs s cccccccccsessscrsscerses SCR MENON UIE CHIEN Pac secncenscnccveneroecececicc cise cessiaccisccucacwsecisce cleslslsiseiees ORPSMORMUIRCEIIN sat cecunciactocccescescecesicceses seclscwesiscasiecciesels) sjecciecisiees UCIGMR = PHATE OMNI UIRGHUN os cn sinscvisiacisesiscnisoscssesesececcecccocinsccosscccee DUMB-BELLS IN HOLOTHOURIA.... eatseees eseciseastars svaeowessane 5 WHEEL IN CHIRODOTA......... 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Muccaceusesccees auc Naccsceceseeccesse SECTION OF SPONGE... weoceesecoeeeess TREIREE-SIDED IUUGLENA:sccccoccccccscescocssss SWAN NECK AND! TTS! DIVISIONSsccccsccssecsscceccsscseasewscdesscsecescasecccen PARAM CECLUM Avensis tvcocecceceschosedsuesenceccerssevacesscetsevcsosscosescbvesesens Se ereercsccsooeresees xii LIST OF ILLUSTRATIONS. © Pacs COLEPS “AND (CHILOMONAS:.... cocedcceecs cus coccoss ves souscueste eee « 455 VORTICELLZ ...... Gia csvocteacecacicessssceseocscuscecescce ran ccser nee Tere eTen «» 459 PA'CINETA cocusccccceneasseccssscssescres Sessebecstencs coecceocsceecosseeees ica shee coves 464 DWIAGINIGOLA \scpscetececesccccscoccescessecetdisnccoteces scebeassaecase aetesces coovee 468 IGUPLOTES scc2sccccessccosece Se scdecesoccecdsees esdocacsdcecseseesee secsosanpevese «- 475 EVENINGS poe EEE “MACHR OSCOPE,. CHAPTER. I HAIRS, FEATHERS, AND SCALES. Nor many years ago an eminent microscopist received a communication inquiring whether, if a minute por- tion of dried skin were submitted to him, he could de- termine it to be Auman skin or not. He replied, that he thought he could. Accordingly a very minute frag- ment was forwarded to him, somewhat resembling what might be torn from the surface of an old trunk, with all the hair rubbed off. The professor brought his microscope to bear upon it, and presently found some fine hairs scattered over the surface; after carefully examining which, he pro- nounced with confidence that they were human hairs, and such as grew on the naked parts of the body; and still further, that the person who had owned them was of a fair complexion. This was a very interesting decision, because the fragment of skin was taken from the door of an old church in Yorkshire ;* in the vicinity of which a tradi- * Tam writing from memory, having no means of referring to the orig- inal record, which will be found in the first (or second) volume of the 1 2 EVENINGS AT THE MICROSCOPE. tion is preserved, that about a thousand years ago a Danish robber had violated this church, and haying been taken, was condemned to be flayed, and his skin nailed to the church-door, as a terror to evil-doers. The action of the weather and other causes had long ago removed all traces of the stretched and dried skin, except that, from under the edges of the broad-headed nails with which the door was studded, fragments still peeped out. It was one of these atoms, obtained by drawing one of the old nails, that was subjected to mi- croscopical scrutiny ; and it was interesting to find that the wonder-showing tube could confirm the tradition with the utmost certainty ; not only in the general fact, that it was really the skin of man, but in the special one of the race to which that man belonged, viz. one with fair complexion, and light hair, such as the Danes are well known to possess. It is evident from this anecdote, that the human hair presents characters so indelible that centuries of exposure have not availed to obliterate them, and which readily distinguish it from the hair of any other creature. Let us then begin our evening’s entertainment by an examination of a human hair, and a comparison of it with that which belongs to va- rious animals. Here, then, is a hair from my own head. I cut off about half an inch of its length, and, laying it between two plates of glass, put it upon the stage of the micro- scope. I now apply a power of 600 diameters ; that is, the apparent increase of size is the same as if six hun dred of these hairs were placed side by side. Now, ‘Transactions of the Microscopical Society” of London. The general facts, however, may be depended on. HAIRS, FEATHERS, AND SCALES. 3 with this eye-piece micrometer, we will first of all ineasure its diameter. You see, crossing the bright circular field of view, a semi-pellucid cylindrical object; that is the hair. You see also a number of fine lines drawn parallel to each other, exactly like those on an ivory rule or scale, with every fifth line longer than the rest, and every tenth longer still. This is the micrometer, or scale by which we measure objects; and the difference in the length of the lines, you will readily guess is merely a device to facilitate the counting of them. By moving the stage up or down, or to either side, we easily get the hair to be exactly in the centre of the field ; and now, by adjusting the eye-piece, we make the scale to lie directly across the hair, at right angles with its length. Thus we see that its diameter covers just thirty of the fine lines ; and as, with this magnifying power, each line represents 1-10,000th of an inch, the hair is 30-10,000ths,=~1.rd of an inch, in diameter. In all branches of natural history, but perhaps pre- eminently in microscopic natural history, —owing to its greater liability to error from illusory appearances,—we gain much information on any given structure by com- paring it with parallel or analogous structures in other forms. Thus we shall find that our understanding of the structure of this hair will be much increased when we have seen, under the same magnifying power, specimens of the hair of other animals. In order, however, to explain it, I must anticipate those ob- servations. HUMAN HAIR, $ EVENINGS AT THE MICROSCOPE. What we see, then, is a perfectly “translucent eyl- inder, having a light brown tinge, and marked with a great number of delicate lines, having a general trans- verse direction, but very irregularly sinuous in their individual courses. These lines we perceive to be on the surface ; because, if we slowly turn the adjustment- screw, the lines grow dim on the central part of the cylinder, while those parts that lie near the edges (speak- ing according to the optical appearance) come into dis- tinctness. Presently the edges of the cylinder become sharply defined, and are seen to be cut into exceedingly shallow saw-like teeth, about as far apart as the lines ; these, however, are so slight that they can be seen only by very delicate adjustment. We go on turning the screw, and presently another series of transverse lines, having the same characters as the former, but differing from them individually, come into view, at the sides first, and presently in the middle, and then, as we still turn, become dim, and the whole is confused. In fact our eye has travelled, in this process, from the nearer sur- face of the hair, right through its transparent substance, to the farther surface ; and we have seen that it is sur- rounded by these sinuous lines, which the edges—or those portions of the hair which would be the edges, if it were split through the middle (for, optically, this is the same thing)—show to be successive coats of the surface, sud- denly terminated. If we suppose a eylinder to be formed of very thin paper, rolled up, and then, with a turning-lathe, this cylinder to be tapered into a very lengthened cone, the whole would be surrounded by lines marking the cut-through edges of the successive layers of paper; and, owing to the thickness of the paper not being mathematically equal in every part, HAIRS, FEATHERS, AND SCALES. 5 these edges would be sinuous; exactly as we see in these lines upon the hair. The effect and the cause are the same in the two cases. A hair is closely analogous to the stem of a plant ; inasmuch as it grows from a root, by continual additions of cells to the lower parts, which, as they lengthen, push ‘forward the ever-lengthening tip. Indeed, in some of the hairs which we shall presently look at, there is the most curious resemblance to the stem of a palm, with the projections produced by the successive growth and sloughing of leaf-bases around the central cylinder. Internally, too, the resemblance is remarkable; for, if we split a human hair, and especially if we macerate it in weak muriatice acid, we shall find it composed of (1) a thin but dense kind of bark, forming the successive overlapping scales just described; (2) a fibrous sub- stance, extending from the bulb to the point of the hair. By soaking the hair in hot sulphuric acid, this fibrous -substance resolves itself into an immense number of very long cells, pointed at each end, and squeezed by mutual pressure into various angular forms. ‘“ A human hair, of one-tenth of a line in thickness,* has about 250 fibrils in its mere diameter, and about 50,000 in its entire calibre: so that these ultimate fibrils are finer than those of almost any other known tissue, from the great elongation and narrowing of their constituent eells as they are drawn out into the shaft of the hair during growth; and hence the expanded bulb of the hair, where the cells are yet spherical and soft.”+ (8) * This is nearly thrice as great as the diameter I had given above, which was the result of several careful admeasurements of different hairs, taken from childhood and adult age. + Grant. Outl. Comp. Anat. 647. 6 EVENINGS AT THE MICROSCOPE. Running through the very centre of the fibrous portion may be sometimes discerned a dark slender line, which is a sort of pith (medulla), composed of minute roundish cells, filled with air, and arranged in two or three rows. loG’s BRISTLE. The bristles of the Hog bear much resemblance to the human hair. On this slide is one, which you per- ceive is just thrice as thick as the hair that we have been examining, or ;1,;th of an inch in diameter. The sinuous lines across the surface are proportionally far finer and closer together, and no saw-teeth are visible at the edge, the most delicate adjustment showing only a minute undulation in the outline; that is to say, the overlapping scales are far thinner, and therefore their terminations are nearer together, in the hair of the Swine than in that of Man. I will now show you a transverse section of a similar bristle, which I will ob- tain thus: I take this old brush, and with a razor cut off one of the bundles of bristles, close to the wood ; then I take off as thin a shaving as I can cut, wood, bristles, and all: I repeat the same operation two or three times. Now, picking out the shavings of wood, HAIRS, FEATHERS, AND SCALES. a [ take up a few of the dust-like atoms with the pvint of my pen-knife, and scatter them on this plate (or slide) of glass, and these I cover with another plate of thin elass ; for this dust is composed of thin transverse slices of the bristles, and as I scatter them, some will fall upon their cut ends, so that we shall look through them endwise. Here is one, very suitable for examination,—since it is not a whole section, the razor having passed some- what obliquely across it, coming out beyond the mid- dle, where it thins away to an cdge. The outline is not circular, but elliptical; that is, the hair is not round, but flattened. There is no separable cortex, or bark, and the whole substance appears made up of exces- sively fine fibres, of which we see the ends cut across. A rough dark line occupies the middle of the slice, in the plane of the greater diameter ; but at the edge of the slice we are able to see that this is not a solid core, as has been sometimes supposed, but a cavity passing up through the hair. It is surrounded by a layer of me- dullary cells, which appear black, because they are filled with air. The finer hairs of the Horse and the Ass, such as those selected from the checks, have the sinuous edges of the plates about as close as in human hair. But they are distinguished at once by the conspicuousness of the medullary portion, which is thick, and quite opaque, and is broken up (especially towards each extremity of the hair) into separate longitudinal irregular masses. The fine wool of the Sheep is clothed with imbrica- tions, proportionally much fewer than those of human hair, while the diameter is also much less. Thus these examples, selected from fine flannel and from coarse 8 EVENINGS AT THE MICROSCOPE. worsted, vary in diameter from ;,';;th to ~1,;th of an inch; and there are, upon an average, about two im- brications in a space equal to the diameter. No colour is perceptible in these specimens; they are as transparent and colourless as glass. The im- bricated plates project here considerably more than in either of the examples we before exam- ined; the “teeth,” however, form an obtuse angle. We shall presently see the importance of this imbricate structure; but we will first look ata few more examples, in which we shall find it still more strongly developed, in conjunction with some other peculiarities. All the hairs that we have looked at are what I have called 4 fibrous in their interior texture, but those of ‘\ many animals are more distinetly cellular. eae Thus, in these specimens, plucked from the suzer'sWtfur of the Cat that les coiled up on the hearth- rug, we see, first, that the imbrications are short, being about equal to the diameter in length, but are very strongly marked; though, like those of the Sheep’s wool, obtuse. Hence, the contour is extremely like that of the stipe of an old rough palin-tree. There is a distinet bark (cortex), which is thick, and marked with longitudinal lines, which add tothe resemblance just al- luded to. The interior is clear, marked off at pretty regular intervals by the broad flattened medullary cells, in single series, each cell occupying, for the most part, the whoie breadth of the interior. These cells are trans- parent and apparently empty; but their walls appear opaque and almost black,—an optical illusion, depen- dent on the absorption of the light by their surfaces at HATRS, FEATHERS, AND SCALES. 9 certain angles with the eye of the beholder. The fibrous portion is here almost displaced by the great development of the medullary cells. In the larger hairs of the Mole, which we will now look at, the bark is very thin; and though the surface is marked with sinuous lines, these do not project into teeth. The pith here again forms the greater portion of the hair, the cells of which it is composed being placed in single series, which, for the most part, extend all across the body of the hair, though they are somewhat irregular | both in size and shape. They are rather flat- tened, and appear perfectly black (that is, opaque) by transmitted light, their surfaces | absorbing all the rays of light. The small sam or car. hairs of the same animal, however, are very different in form : they are flattened, so as to appear twice as broad “In one aspect as in pasthon at Ay right angles to it; and, what is (iin? curious, Aa cals os the Be ea. perceptible on the \ other. Here, as in the larger i hairs, there is a single row of f# oval transverse cells, perfectly \ opaque. The hair of many of the @ " M) smaller Mammalia shows con- "4 siderable diversity of form, ac- cording to the part which we select for observation. Thus, if we take a long hair out of this Sable tippet, 1* MAIRS OF MOLE. 10 EVENINGS AT THE MICROSCOPE. and examine it near the base, we see that it is very slender, transparent, and colourless, covered with strongly-marked imbrications, which are not obtuse teeth, but long, pointed, overlapping scales, about ten of which complete a whorl. The fibrous portion is moderately thick; inclosing a wide pith of roundish cells, set in two rows, that allow the rays of light to be transmitted through their central parts. As we trace the hair upwards, by moving the stage of the microscope, by and by it swells and rapidly in- creases in thickness; the imbrications are scarcely per- | ceptible ; while the pith- cells have greatly augment- edinnumber andin breadth. These are arranged in con- | fused, close-set, transverse ' rows, and are nearly opaque. Still tracing up the same hair, as we approach the tip, the bark and fibrous part become very thin ; the cells are fewer and fewer till they cease altogether, and a long slender point, of a clear yellow tinge, NAIR OF SABLE. without cells, presents transverse wavy lines of imbri- cation scarcely projecting. The hair of the common Mouse is a pretty and in- teresting object. In the larger specimens the fibrous portion is reduced almost to nothing. The imbrications project very little, but careful observation reveals slant- ing lines proceeding from the “teeth ; ” which show that the whole surface is clothed with long pointed ILAIRS, FEATHERS, AND SCALES. tf scales, which are excessively thin, and lie close. The pith consists of large flattened cells, arranged thus : one row passes up through the cen- yz tre, and other similar ones are set in ey ss a circle around it, so that a longitu- | dinal section would show three par- { 4 allel rows. These cells are translu- |) cent, and some of them are either | wholly or partially lined with a clear }/ yellow pigment. The smaller hairs from the same little animal are scarcely }i distinguishable from those of \ the Cat, already described, ex- cept that the imbrications are proportionally larger. In all, the extremity is drawn out to a lengthened fine point, and is occupied with clear yellow cells, except the very tip, which is colourless, and imbricated with sinuous j whorls, each consisting of a single scale. But it is in the Bats that the imbricated | character attains its greatest development. { On this slide is a number of hairs from the fur of one of our English Bats, in which it is far more conspicuous than in any example we have yet seen. In the middle portion of each | hair the scales lie close, embracing their suc- fal cessors to the very edges, or nearly ; but the ‘ lower part, which is more slender, resembles np or 2Multitude of trumpet-shaped flowers formed™4!™ oF namorilto a chain, each being inserted into the wows throat of another. The lip of the “flower” is generally oblique, and here and there we can perccive MAIR OF MOUSE. 12 EVENINGS AT THE MICROSCOPE. that each is formed of two half-encircling scales ; for one scale occasionally springs from the level of its fel- low, so as to make the imbrication alternate. Even this, however, is far excelled by a species of Bat from India, of whose hair I have now specimens on the stage. The trumpet-like cups are here very thin and transparent, but very expansive; the diameter of the lip being, in some parts of the hair, fully thrice as great as that of the stem itself. The margin of each eup appears to be undivided, but very irregularly notched and cut. In the middle portion of the hair, the cups are far more crowded than in the basal part, more brush- like, and less elegant; and this structure is continued to the very extremity, which is not drawn out to so at- tenuated a point as the hair of the Mouse, though it is accident ; for in these dozen hairs there are several, in which we sce one or more cups rubbed off, and in one the stem is destitute of them for a consid- erable space. The stem so dennded closely resembles the basal part of a Mouse’s hair in its normal condition. This character of being clothed with overlapping scales, each growing out of its predecessor, is common, then, to the hairs of the Mammalia, though it exists in different degrees of development. It inay be readily detected by the unaided sense, even when the eye, though as- sisted by the microscope, fails to recognise it. WINGS AND THEIR APPENDAGES. 105 Though he regards these laminz as the cause of hum- ming in bees and flies, he does not decide that other causes may not produce the buzz of cockchafers, &e., in the thoracic spiracles of which he could not discern them.* * Man. of Entom. 468. 5* 106 EVENINGS AT THE MICRCSOOPE. CHAPTER VI. INSECTS ! THEIR BREATHING ORGANS. In order to understand the passage last quoted from Burmeister, you ought to know something of the man- ner in which breathing is performed among insects. Essentially, breathing is the same function, wherever it occurs; and it does occur, doubtless, in all animals under some form or other. It is the absorption of oxy- gen from without to the fluids within, to repair the waste constantly produced by vital energy. But it may be obtained from different sources, and imbibed in various modes. All insects in the perfect state are air-breathers ; that is, they procure their oxygen from the air as we do; and most of them are so in their earlier stages. Even in exceptional cases, viz., such larvee or pupee as are provided with what represent gills, and appear te be dependent on the water for their respiration, the exception is rather apparent than real, for the function 1s performed in air-vessels still. Now these air-vessels shall afford us some interesting microscopical obser vations. This brown fly, which is buzzing and hovering on invisible wings over the flowers in the garden, you perhaps take fora bee. No; it has but two wings; INSECTS: THEIR BREATHING ORGANS. 107 for 1 have caught it, and you may ascertain the fact for yourself; it belongs to the genus Syrphus. Havy- ing caught it, I deprive it of life by means of the very organs I am going to examine, for I turn a tumbler over it and insert under the edge a lighted lucifer- match. In a few seconds it is dead,—sutfocated ; for phosphoric and sulphuric acids introduced into the breathing tubes quickly destroy life. I presently take it out, and putting it into a dissecting-trough under a lens, cut up the abdomen with a pair of fine pointed scissors. Then I pin open the divided abdomen to the bottom of the trough, which is coated with wax for the purpose; and, looking at it with the lens—but you shall look for yourself. Well, you see little else but the polished brown walls of the body and a number of fine white threads. It is those threads that we want. With a small camel’s hair pencil I move them to and fro in the water, and soon perceive that they are like little trees with com- paratively thick trunks, sending off many branches, and eradually becoming excessively slender. Here and there short thick branches break out on two opposite sides, and on each side are connected with the wall of the abdomen. Here then with the fine scissors I snip them across, and lift up a portion with the hair pencil into a drop of water which I have already put into the live-box. The cover now flattens the drop, spreads the white threads,—and the object is ready for our eye. We haye before us a considerable portion of the tracheal system of the fly. And though, owing to the involution of the parts and the injury our rude anatomy has done, we cannot trace the beautiful regularity 198 EVENINGS AT THE MICROSCOPE. which exists in life, we may see the principle on which they are arranged, and much of the perfection with which they are constructed. Here then is a system of pipes,—some large, some small; the smaller branching forth from the large, and themselves sending off yet smaller branches, which in their turn divide and subdivide until the final rami- fications are excessively attenuated. esides these, we see here and there ovate or barrel-shaped reservoirs, having the same appearance and intimate structure as the pipes, but of much larger calibre and connected with them by a branch. This, I say, is the breathing system, or a large por- tion of it. These pipes receive the air from without through trap-doors, which we will examine presently, and convey it to the most distant parts of the body. In ourselves the air is inhaled into a great central reser- voir, the lungs, and the blood dispersed through every part is brought to this reservoir to be oxygenated. In insects it is the blood that is collected into a great central reservoir, and the air is distributed by a mi- nutely divided system of vessels over the blood-reser- voir. The trachee or air-pipes have a silvery white ap- pearance by reflected light ; but if we use transmitted light and put on a high power, we discern a wonderful structure, which I will describe in the eloquent lan- cuage of Professor Rymer Jones, and you shall estimate its truth as you examine the object :— “There is one elegant arrangement connected with the breathing-tubes of an insect specially worthy of ad- miration ; and perhaps in the whole range of animal mechanics it would be difficult to point out an example INSECTS: THEIR BREATHING ORGANS. 109 of more exquisite mechanism, whether we consider the object of the contrivance or the remarkable beauty of the structure employed. The air-tubes themselves are necessarily extremely thin and delicate ; so that on the slightest pressure their sides would inevitably collapse and thus completely put a stop to the passage of air AIR-PIPE OF FLY. through them, producing, of course, the speedy suffoca- tion of the insect, had not some means been adopted to keep them always permeable ; and yet to do so, and at the same time to preserve their softness and perfect flexibility, might seem a problem not easily solved. The plan adopted, however, fully combines both these requisites. Between the two thin layers of membrane which form the walls of every air-tube, a delicate elastic thread (a wire of exquisite tenuity) has been interposed, which, winding round and ronnd in close spirals, forms by its revolutions a cylindrical pipe of sufficient firm- ness to preserve the air-vessels in a permeable condi- tion, whilst at the same time it does not at all interfere with its flexibility ; this fine coil is continued through every division of the ¢rachew, even to their most minute L10 EVENINGS AT THE MICROSCUPE. ramifications, a character whereby these vessels are readily distinguishable when examined under the mi- croscope.* Man has imitated this exquisite contrivance in the spiral wire spring which lines flexible gas-pipes; but his wire does not pass between two coats of membrane. One of the most interesting points of the contrivance is the way in which the branches are (so to speak) in- serted in the trunk, the two wires uniting without leay- ing a blank. It is difficult to describe how this is done; but by tracing home one of the ramifications you may see that it is performed most accurately,— the circumvolutions of the trunk-wire being crowded and bent round above and below the insertion (like the grain of timber around a knot), and the lowest turns of the branch-wire being suitably dilated to fill up the hiatus. You must not suppose, however, that the whole of one tube is formed out of a single wire. Just as ina piece of human wire-work the structure is made out of a certain number of pieces of limited length, and join- ings or interlacings occur where new lengths are intro- duced, so, strange to say, it seems to be here. It is strange, I say, that it should be so, when there can be no limit to the resources, either of material, or skill to use it; but so it is, as you may see in this specimen, which has been dissected out of the body of a silkworm. The spiral is much looser here than in the air-tube of the fly, the turns of the wire being wider apart; and hence its structure is much more easily traced. Ilere you see in many places the introduction of a new wire, always commencing with the most fine-drawn point, * Nat. Hist. of Anim. i. 6. INSECTS: THEIR BREATHING ORGANS. 111 but presently taking its place with the rest so as to be undistinguishable from them. In some cases certainly (perhaps this may be the explanation of the phenome- non in all) the wire so introduced may be found to ter- minate with the like attenuation before it has made a single volution, and seems to be inserted when the per- manent curvature of the pipe would leave the wires on the outer side of the curve too far apart, half a turn, or even much less, then being inserted of supernumerary wire. I told you that the air enters these tubes through certain “trap-doors.” This is not the term which the physiologist employs, certainly: he calls them spiracles. In our own bodies the air enters only at one spiracle, a curiously defended orifice opening just in front of the gullet at the back of the mouth. But in the class of animals we are now considering there are a good many _ such breathing orifices. You may see them to great advantage in any large caterpillar, the silkworm for example, where all along the sides of the pearl-grey body you perceive a row of dots, which with a lens you discover to be little oval disks sunken into little pits, of a black hue with a white centre, through which is a very slender slit. There are nine of these organs on each side, a pair to each segment or divis- ion of the body, with the exception of the first, which is the head, and of the third and fourth, which are destined to bear the wings ; these are destitute of spir- acles. Essentially, these organs, under whatever modifica- tions of form and position they may appear, have the same structure. They are narrow orifices, with two lips capable of being opened at the will of the animal, 119 EVENINGS AT THE MICROSCOPE. or accurately closed ; and in many soft-skinned insects, such as the silkworm, and most larvee, they are set in a horny ring, by which means they are prevented from collapsing, through the unresisting character of the general integument. The opening and shut- ting of them is performed by an internal apparatus of muscles, which is sometimes strengthened by being attached to two horny plates, which project inwardly. But the most curious thing to be noted in the structure of these spiracles is the con- trivance which induced me to call them trap-doors. Small as are their openings, they are still large enough to ad- mit many floating particles of dust, soot, and other extra- neous matters, which would tend to clog up the delicate air-passages, and to impede the right performance of their important functions. Hence they need to be guarded with some sort of sieve, or filter, which, while admitting the air, shall exclude the dust. Various and beautiful are the modes in which this common purpose is effected, but I can show you only two or three. This is one of the breathing orifices of the common House-fly, in which, as you see, minute processes grow from the margin all round, which ex- tend partly across the open area, branching and rami- fying again and again, and spreading and interlacing with those of the opposite side, so as to form a perfect SPIRACLE OF FLY. INSECTS: THEIR BREATHING ORGANS. 1138 sieve, which the finest atoms of dust cannot pene trate. The same end is attained, in another way, in the dirty cylindrical grub, which is found so abundantly at the roots of grass in pasture lands, and which country folk call, from the toughness of its skin, “ leather-coat.” It is the larva of the Crane-fly (Zipula oleracea), so familiar to us under the souwbriquet of Daddy Long-legs. I can easily procure one of these, for, unfortunately, they are but too ubiquitous. Here is one, who shall have the honour of being martyred for the benefit of science. Before we assassinate him, however, just look here, at the hinder extremity of his body, where there is an area, surrounded and protected by several points, and in this area, two black spots. With the dissecting-scissors I have carefully cut out one of these specks, and now I put it under the Lieber- _kuhn, for illumination on the stage of the microscope. There is, first of all, a dark horny ring of an oval figure, a little way within which there is an opaque, dark plate of the same figure, but smaller, occupying the central portion of the area. The space between the margin of the plate and the bounding ring is occupied by a series of slender filaments, placed side by side, proceeding from one to the other, through the interstices of which the air is filtered. The central plate seems to be quite imperforate. The fat, thick-bodied grubs of those beetles called chaters, exhibit, in their spiracles, a modification of this structure, rendered still more elaborate. In the case of the larva of the common Cockchafer (JLelolontha vulgaris), for example, the central plate is a projection from one side of the margin of the spiracle—to use a 114 EVENINGS AT THE MICROSCOPE. geographical simile, we may say that, instead of being an island in the midst of a lake, it is a promontory. SPIRACLE OF LEATHER-COAT. Thus, the breathing space is a . crescent-shaped band, which is crossed in every part by bars passing from the margin to the projecting plate. But, as if the interstices left by these bars would be too coarse for the pur- pose, they are further sublimat- ed by a membrane, which is < stretched across them, and which is perforated with a num- ber of excessively minute round holes, through which alone the air is admitted. In many of the two-winged flies, which inhabit the water in their earlier stages, there are some interesting SPIRACLE OF COCKCHAFER-GRUB. contrivances and modifica- tions connected with the or- gans of respiration. It is ne- cessary that the orifices of the air-tubes should be brought at intervals to the surface of the water, in or- der to come into contact with the external air; while, at the same time, it is im- portant that as small a por- tion as possible of the ani- mal’s body be exposed to danger, by being protruded from its sheltering element. An example in point you may see in this vase. Here is a slender worm, an inch and a half in INSECTS : THEIR BREATHING ORGANS. PLa length, thickest a little behind the head, and tapering gradually to a lengthened tail, the twelve segments of the body being very conspicuous. It swims up and down or to and fro in the clear water, with a not very rapid, wriggling movement, throwing its body alternately from side to side in the form of the let- ter S. This is the maggot of a handsome dipterous fly, sometimes called the Chameleon-fly (Stratiomys cham- wleon). There is much about it to reward observation and careful examination with a low magnifying power, especially the head, with its pointed snout, and its pair of foot-like palpi. These are situated one on each side of the head, are three-jointed, the last joint being studded with short stiff spines, and the second having a thumb-like projection. With these organs, the grub roots and burrows among the decaying vegetable mat- ter at the bottom for its food ; and when not so engaged, they are often rapidly vibrated in a singular manner, the sight of which might induce a feeling of fear, as it they were threatening weapons of offence,—a pair of poisonous stings, for instance; they have, however, no such function, the poor grub being perfectly harn- less. What I wish you chiefly to observe, however, is the tail, with its curious organization. With the naked eye, you can perceive that the last joint is much slend- erer and more lengthened than the rest, and that it is tipped with a beautiful crown of feathers, like the diadem of some semi-savage prince. This is best seen when the animal comes to the surface, which it always does tail uppermost, for as soon as the tip reaches the air, the plumes instantly open, and form an ex: {16 EVENINGS AT THE MICROSCOPE. quisite cone or funnel, from which every drop of moisture is excluded, though the water stands around at the level of the brim. A few seconds it remains motionless thus, the whole body hanging downwards, suspended from the caudal coronet, then suddenly the tips of the plumes curve inward toward each other, inclosing a globule of air, and the animal wriggles away into the depths, carrying its burden, like a pearl, or a glittering bubble of quicksilver, behind it. This you may observe with the unassisted sight, and you may mark, also, how, from time to time, a por- tion more or less, of the bubble of gleaming air is in- haled or expired by the animal, causing a diminution or increase of its volume; and this of itself would con- vince you that it is the spiracles of the animal which are thus protected. The application of a low magnifying power, say from thirty-five to fifty diameters, for we can hardly use a higher magnification than this to the animal while alive, will reveal a few more of the details. We see, then, that the extremity of the last segment forms a circular disk hollowed in the centre, where it is perforated with the two orifices of the air-pipes. The margin of this disk carries about thirty stiff but slender spines or bristles, some of which are branched in a forked manner. Lach bristle bears, on its two opposite sides—viz., on those aspects which face the next bristle on either hand,—two series of not very close-set branch- lets, set like the plumes of a feather, or the pinne of a fern-leaf, which give it the elegant plumose appearance which the unassisted eye recognises. The bristles have a granulose surface near the extremity, and terminate in fine points. INSECTS : THEIR BREATHING ORGANS. 117 The curious faculty of repelling water, which the interior surface of this plumy coronal possesses, is of the highest value in the economy of the insect ; for, on the one hand, it permits the breathing orifices to be brought into contract with the air, even when nearly a quarter of an inch below the surface ; and on the other hand, it allows the volume of air inclosed within the funnel to be perfectly isolated and carried securely away, as a reservoir for the wants of the animal, when engaged in its avocations of necessity or pleasure, in the recesses of its sub- aquatic groves. It is re- markable that so complete is this repellent power, that when the tail is at the sur- face, the animal may make a very perceptible descent without breaking the con- tinuity of the air, the sur- face presenting the curious phenomenon of a deep fun- nel-shaped dimple leading down to the tail of the animal. The chameleon-fly is not, however, so abundant and so universally distrib- uted as that you may al- ways calculate upon being able to repeat these obser- GRUB OF CILAMELEON-FLY. vations when you will. I shall, therefore, show you an analogous example, much more easily obtained. Both 118 EVENINGS AT THE MICROSCOPE. are inhabitants of our fresh waters: the chameleon-grub lives in ponds, crawling among the stems of aquatic plants, and occasionally visiting the surface in the man- ner you have seen; but it is precarious—in some sea- sons not uncommon, in others, scarcely to be met with by the most persevering search. For my next specimen, I have but to go with a basin to the water-butt in the yard, and take a dip of the surface-water at random: I shall be pretty sure of a score at least. Here they are swarming, as I told you. What, those things? why, they are gnat-grubs. Well, don’t despise them, you will find them worth looking at. I dare say you have never submitted them to half-an- hour’s microscopical examination. I have caught one with a spoon, and put it into this narrow glass trough of water that it may rest conveniently on the stage. We will take a cursory glance at its entire person. Here is a flat, roundish head, a great globose, swollen thorax, and a long, slender, many-jointed body, ending in a curious fork. But all is curious :—the head, with its horny transparency ; its pair of rod-like antenna, covered with minute points ; its two black eye-patches ; and its jaws, beset with strong, curved hairs, set in radiating rows, and, ever and anon, working to and fro with the most rapid vibrations :—the thorax,—so trans- parent, with its amber-like clearness, that you can dis- cern the dorsel vessel, which contains the blood ever dilating and collapsing with the most beautiful regular- ity ; and, beneath this, the gullet, through which, now and then, descends a dark pellet of food, to join the mass already lodged in the stomach farther down,—a result, by the way, that explains that incessant vibra- tion and pumping motion of the mouth-organs, which INSECTS : THEIR BREATHING ORGANS. 119 thus evidently are engaged in collecting food from the water ; though, even with this power, we can see no solid matter taken in, till we discern it agglomerated in the swallowed pellets :—the body, or abdomen, with its ten joints, all (with a slight exception) the counterparts of each other; and each carrying its own dilatation of the dorsal vessel, and its own portion of the long and well-filled intestinal canal :—all these, I say, are very interesting and curious to observe ; especially when we select, as I have done, a young individual for examina- tion; since the tissues then possess a translucency which is essential to our seeing with distinctness any- thing of the internal organization, but which soon gives place to opacity, as the insect advances in age. Very curious, too, are the hairs with which the whole surface of the animal is furnished at certain de- terminate points. But these are seen to more advan- tage in an older specimen; for, in this one of tender hours, they are nearly simple; whereas, in an opaque, nearly full-grown individual, every hair is seen to be studded with secondary points, that project from its surface throughout its length. These hairs are arranged in beautiful radiating pencils or tufts, and scattered, as I have said, at definite points over the whole body ;— there is a tuft on each antenna; one on the forehead ; one in front of each eye-spot; several circles of them set round the thorax; one circle of scanty pencils set round each segment of the body, and a few smaller tufts scattered about besides; all of them springing from minute round warts. The extremity of the abdomen deserves, however, a separate investigation, and we will now direct our at- tention to the tail-end of our tiny grub. There are ten 120 EVENINGS AT THE MICROSCOPE. segments to the abdomen; at the eighth it seems to divide into two branches, one longer than the other. This appearance, however, is due to the circumstance that the respiratory tube is sent forth from the eighth segment, and that the ninth and tenth segments are bent away at an angle from the general line of the body. The ninth segment is very small: the tenth is squar- ish, with rounded corners, and is brought to a thin edge. Around the margin there is the most exquisite array of hairs possible; at one corner there are three pencils ; while round the opposite, and down the cor- responding side, run in two rows twelve pencils, set very close to each other, and each containing a large number of very slender hairs. The extreme end of the segment is ornamented with four diverging organs of taper conical form and crystalline clearness, through the midst of each of which passes a very fine branch of the air-tube system, which gives off still more at- tenuated branchlets in its course. We have not yet, however, examined the origin of this air-breathing system. There is but one en- trance to the air, or rather two placed close together, at the end of that round column, which is sent off from the eighth segment of the abdomen. This column, which is roughened all over with minute points, and fringed with rows of hairs, ends in a horny, conical »oint, which seems entire while under water, but no sooner does it come to the surface, than it is seen to split into five triangular pieces, which open widely, and expose a hollow, at the bottom of which are the two spiracles. From these the two main air-pipes are seen to com INSECTS : THEIR BREATHING ORGANS. 121 mence aud to proceed along the centre of the column, thence into the abdomen, which they traverse one along each side, sending off slender branchlets all along, and becoming more and more attenuated themselves ; till, at length, we trace them into the thorax, and thence through the slender neck into the head itself, until they terminate in fine points close to the back of the mouth, It needs, it is true, a very transparent specimen to fol- low the tracheal tube thus through their entire course ; but in such it can be done without difficulty. And it is very instructive to do so, inasmuch as one such per- sonal examination of an insect under a good microscope will make you far more familiar with the peculiarities of its physiology, than the clearest book-descriptions, or even the best and most elaborate plates, alone. Perhaps you may think I have kept you too long over these gnat-grubs, but my reason for being more minute in the examination of this creature is, that its extreme abundance in every place, and through the greatest part of the year, puts it in the power of every- one to procure a specimen alive and healthy, almost whenever he chooses, and, therefore, it is peculiarly available for microscopic study ; while the transparency - of its tissues, and its generally simple organization, make it a more than usually suitable object for investi- gation: besides which, there are the beautiful and in- teresting points in the details of its structure which I have been endeavouring to bring before you. Not less interesting and remarkable is the change in the position of the spiracles, which takes place as soon as this grub arrives at the pupa or chrysalis state. The skin of the active, fish-like larva splits down the back, and out presses an equally active little monster; 6 122 EVENINGS AT THE MICROSCOPE. which, if you did not know it, you would never think of connecting with the grub from which it has pro- ceeded ; so totally different is it in form, in structure, and in motions. We shall easily find some in our basin that have passed into this stage. Yes, here is one, which will please to take its place in the glass trough with its younger brothers. How strange the transformation ! It reminds us of a lobster, though, of course, the re- semblance is only cursory. With the naked eye we see that the thorax is greatly enlarged, not only ac- tually, but proportionally ; that it forms an oval mass, occupying some five-sixths, at least, of the entire ani- mal; the rest apparently being taken up by a slender, many-jointed abdomen, which curves round the great thorax, and, bending under it, ends in an excessively delicate, transparent, swimming-plate. It is this curving abdomen, with its terminal swimmer, and its back- ward strokes in swimming, that constitute the resem- blance to a prawn or lobster. If we now bring a low power with the reflected light of the Lieberkuhn to bear on it, we shall see the progress the animal has made in this its change of rai- nent. The thorax shows on its sides the future wings, ernmpled and folded down, the nervures of which we can discern distinctly. The elegant little head, too, can be well made out; its eyes, now perfectly marked with the numerous hexagonal facets that belong to the ma- tured organs of vision in these creatures; its antenn, like slender rods, folded down side by side along the inferior edge of the thorax; the short palpi lying out- side these; and within, both the lancets and piercers that are destined to subserve the blood-sucking propen- INSECTS : THEIR BREATHING ORGANS. 123 sities of our sanguinary little subject, when it attains its winged condition ;—all encased in the transparent pupa skin, that lies like a loose wrapper around every- thing. The extremity of the abdomen has now nothing to do with respiration, and hence it is never brought to the surface of the water, as it was constantly before. The little animal still habitually lives in contact with the air, coming up to it with rapid, impatient jerks, whenever it has descended; but it is invariably the summit of the thorax that is uppermost, and when the creature rests, it is this part that touches the sur- face. Why is this? you ask. Look, and you will see why. From the summit of the thorax project two little horns, which, under the microscope, are seen to be clear trumpet-shaped tubes with open mouths, cut as it were obliquely off. These enter the thorax close to the bases of the wings ; and when we confine the animal in a glass cell, exercising a gentle pressure upon the thor- ax, we see bubbles of air alternately projected from the trumpet mouths of the tubes and sucked in again. These, then, are the spiracles, the orifices of the air-tubes, where the vital fluid enters the body, and whence it is carried to every part of the system. There is something curiously beautiful about the structure of these spiracular tubes, of which I cannot attempt to explain the object. With a high magnifying power, their whole exterior surface is seen to be covered with regular rounded scales, overlapping each other, and very closely resembling those of a fish. 124 EVENINGS AT THE MICROSCOPE. CHAPTER vail: INSECTS! THEIR FEET. I wave here inclosed a small window-fly in the live box of the microscope, that you may examine the struc- ture of its fect as it presses them against the glass cover ; and thus not only get a glimpse of an exquisitely-formed structure, but acquire some correct ideas on the ques- tion of how a fly is enabled to defy all the laws of physics, and to walk jauntily about on the under sur- face of polished bodies, such as glass, without falling, or apparently the fear of falling. And a personal examin- ation is the more desirable because of the hasty and er- roneous notions that have been promulgated on the matter, and that are constantly disseminated by a herd of popular compilers, who profess to teach science by gathering up and retailing the opinions of others, often without the slightest knowledge whether what they are reporting is true or false. The customary explanation has been that given by Derham in his “ Physico-theology ;” that “ divers flies and other insects, besides their sharp-hooked nails, have also skinny palms to their feet, to enable them to stick to glass, and other smooth bodies, by means of the pres- sure of the atmosphere, after the manner as I have seen boys carry heavy stones, with only a wet piece of lea- INSECTS : THEIR FEET. 125 ther clapped on the top of a stone.” Bingley, citing this opinion, adds that they are able easily to overcome the pressure of the air “in warm weather, when they are brisk and alert; but towards the end of the year this resistance becomes too mighty for their diminished strength ; and we see flies labouring along, and lugging their feet on windows as if they stuck fast to the glass: and it is with the utmost difficulty they can draw one foot after another, and disengage their hollow cups from the slippery surface.” * But long ago another solution was proposed: for Hooke, one of the earliest of microscopic observers, de- scribed the two palms, pattens, or soles (as he calls the pulvillr), as “ beset underneath with small bristles or tenters, like the wire teeth of a card for working wool, which, having a contrary direction to the claws, and both pulling different ways, if there be any irregularity or yielding in the surface of a body, enable the fly to ‘suspend itself very firmly.” He supposed that the most perfectly polished glass presented such irregular-— ities, and that it was moreover always covered with a ‘smoky tarnish,” into which the hairs of the foot pene- trated. The “smoky tarnish” is altogether gratuitous; and Mr. Blackwall has exploded the idea of atmospheric _ pressure, for he found that flies could wall up the in- terior of the exhausted receiver of an air-pump. He had explained their ability to climb up vertical polished bodies by the mechanical action of the minute hairs of the inferior surface of the palms; but further experi. ments having showed him that flies cannot walk up glass which is made moist by breathing on it, or which * Anim. Biogr. 126 EVENINGS AT THE MICROSCOPE. is thinly coated with oil or flour, he was led to the con- clusion that these hairs are in fact tubular, and excrete a viscid fluid, by means of which they adhere to dry polished surfaces ; and on close inspection with an ade- quate magnifying power, he was always able to dis- cover traces of this adhesive material on the track on glass both of flies and various other insects furnished with pulvilli, and of those spiders which possess a sim- ilar faculty.* In the earlier editions of Kirby and Spence’s “ In- troduction to Entomology,” Mr. Kirby had adopted the suctorial hypothesis. But in a late one he made an al- lusion to Mr. Blackwall’s opinion, and added the follow- ing interesting note :— “On repeating Mr. Blackwall’s experiments, I found, just as he states, that when a pane of glass of a window was slightly moistened by breathing on it, or dusted with flour, bluebottle-flies, the common house- flies, and the common bee-fly (Z7istalis tenax) all slipped down again the instant they attempted to walk up these portions of the glass ; and I moreover remarked that each time after thus slipping down, they immedi- ately be ganto rub first the two fore tarsi, and then the two hind tarsi, together, as flies are so often seen to do, and continued this operation for some moments before they attempted again to walk. This last fact struck me . very forcibly, as appearing to give an importance to these habitual procedures of flies that has not hitherto, as far as Iam aware, been attached to them. These movements I had always regarded as meant to remove any particle of dust from the legs, but simply as an affair of instinctive cleanliness, like that of the eat when * Linn. Trans. xvi. 490, 748. INSECTS : THEIR FEET. 127 she licks herself, and not as serving any more important object; and such entomological friends as I have had an opportunity of consulting tell me that their view of the matter was precisely the same ; nor does Mr. Black- wall appear to have seen it in a different light, since, though so strongly bearing on his explanation of the way in which flies mount smooth vertical surfaces, he never at all refers to it. Yet, from the absolute neces- sity which the flies on which I experimented appeared to feel of cleaning their pulvillz immediately after being wetted or clogged with flour, however frequently this securred, there certainly seems ground for supposing that their usual and frequent operation for effecting this by rubbing their tarsi together is by no means one of mere cleanliness or amusement, but a very important part of their economy, essentially necessary, for keeping their pulvilli in a fit state for climbing up smooth ver- tical substances by constantly removing from them all moisture, and still more all dust, which they are per- petually liable to collect. In this operation the two fore and two hind tarsi are respectively rubbed together for their whole length, whence it might be inferred that the intention is to remove impurities from the entire tarsi; but this I am persuaded is not usually the ob- ject, which is simply that of cleaning the under side of the pulvilla by rubbing them backward and forward along the whole surface of the hairs with which the tarsi are clothed, and which seem intended to serve as a brush for this particular purpose. Sometimes, indeed, when the hairs of the tarsi are filled with dust through- out, the operation of rubbing them together is intended to cleanse these hairs; because, without these brushes were themselves clean, they could not act upon the 128 EVENINGS AT THE MICROSCOPE. hairs of the under side of the pulvilli. Of this I wit- nessed nn interesting instance in an Lristalis tenaz, which by walking on a surface dusted with flour had the hairs of the whole length of the tarsi, as well as the pulwili, thus clogged with it. After slipping down from the painted surface of the window-frame, which she in vain attempted to climb, she seemed sensible that before the puivillz could be brushed it was requi- site that the brushes themselves should be clean, and full two minutes were employed to make them so by stretching out her trunk, and passing them repeatedly along its sides, apparently for the sake of moistening the flour and causing its grains to adhere ; for after this operation, on rubbing her tarsi together, which she next proceeded to do, I saw distinct little pellets of flour fall down. A process almost exactly similar I have always seen used by bluebottle-flies and common house- flies which had their tarsi clogged with flour by walk- ing over it, or by having it dusted over them; but these manceuvres are required for an especial purpose, and on ordinary occasions, as before observed, the ob- ject in rubbing the tarsi together is not to clean them, but the pulvilli, for which they serve as brushes. Be- sides rubbing the tarsi together, flies are often seen, while thus employed, to pass the two fore tarsi and tibiz with sudden jerks over the back of the head and eyes, and the two hind tarsi and tibize over and under the wings, and especially over their outer margins, and occasionally also over the back of the abdomen. That one object of these operations is often to clean these parts from dust, I have no doubt, as on powdering the flies with flour they thus employ themselves, sometimes for ten minutes, in detaching every part of it from INSECTS: THEIR FEET. 129 their eyes, wings, and abdomen ; but I am also inclined to believe that, in general, when this passing of the legs over the back of the head and outer margin of the wings takes place in connexion with the ordinary rub- bing of the tarsi together, as it usually does, that the object is rather for the purpose of completing the entire cleansing of the tarsal brushes (for which the row of strong hairs visible under a lens on the exterior margin of the wings seems well adapted), so that they may act more perfectly on the pulvilli. Here, too, it should be noticed, in proof of the importance of all the pulvillt being kept clean, that as the tarsi of the two middle legs cannot be applied to each other, flies are constantly in the habit of rubbing one of these tarsi and its pulvilli, sometimes between the two fore tarsi, and at other times between the two hind ones. .... “Though the above observations, hastily made on the spur of the occasion since beginning this note, seem to prove that it is necessary the pulvilli of flies and of some other insects should be kept free from moisture and dust to enable them to ascend vertical polished surfaces, they cannot be considered as wholly settling the question as to the precise way in which these pul- villa, and those of insects generally, act in affecting a similar mode of progression; and my main reason for here giving these slight hints is the hope of directing the attention of entomological and microscopical ob- servers to a field evidently, as yet, so imperfectly ex- plored. “ After writing the above, intended as the conclu- sion of this note, I witnessed to-day (July 11, 1842), a fact which I cannot forbear adding to it. Observing a house-fly on the window, whose motions seemed very G* 130 EVENINGS AT THE MICROSCOPE. strange, I approached it, and found that it was making violent contortions, as though every leg were affected with St. Vitus’ dance, in order to pull its pulvillz from the surface of the glass, to which they adhered so strongly that though it could drag them a little way, or sometimes by a violent effort get first one and then another detached, yet the moment they were placed on the glass again, they adhered as if their under side were smeared with bird-lime. Once it succeeded in dragging off its two fore legs, when it immediately began to rub the pulvilli against the tarsal brushes; but on replacing them on the glass they adhered as closely as before, and it was only by efforts almost con- vulsive, and which seemed to threaten to pull off its limbs from its body, that it could succeed in moving a quarter of an inch at atime. After watching it with much interest for five minutes, it at last by its con- tinued exertions got its feet released and flew away, and alighted on a curtain, on which it walked quite briskly, but soon again flew back to the window, where it had precisely the same difficulty in pulling its pu/- villi from the glass as before; but after observing it some time, and at last trying to catch it, that I might examine its feet with a lens, it seemed by a vigorous effort to regain its powers, and ran quite actively on the glass, and then flying away I lost sight of it. Iam unable to give any satisfactory solution of this singular fact. The season, and the fly’s final activity, preclude the idea of its arising from cold or debility, to which Mr. White attributes the dragging of flies’ legs at the close of autumn. The pulvilli certainly had much more the appearance of adhering to the glass by a vis- cid material than by any pressure of the atmosphere, INSECTS: THEIR FEET. 151 and it is so far in favour of Mr. Blackwall’s hypothesis, on which one might conjecture that from some cause (perhaps of disease) the hairs of the pudvzllz had poured out a greater quantity of this viscid material than usual, and more than the muscular strength of the fly was able to cope with.” * In the foot of the fly under our own observation you may see how well the joints of the tarsus are covered with hairs, or rather stiff pointed spines, of various dimensions and distances apart, and hence how suitable these are for acting the part of combs to cleanse tle palms. But these last are the organs that most claim and deserve our examination. In the specimen of the little Musca that I have imprisoned, the last tarsal joint is terminated by two strong divergent hooks which are themselves well clothed with spines, and by two membranous flaps or palms beneath them. These are nearly oval in outline, though in some species they are nearly square, or triangular, and in some of a very irregular shape. They are thin, membranous, and transparent, and when a strong light is reflected through them by means of the achromatic condenser, we see their structure under this power of 600 diameters very distinctly. The inferior surface of the palm, on which we are now looking, is divided into a vast number of lozenge- shaped areas, which appear to be scales overlapping each other, or they may be divided merely by depressed lines. From the centre of each area proceeds a very slender, soft, and flexible pellucid filament, which reaches downwards to the surface on which the fly is walking, and is there slightly hooked and enlarged into * TIntr. to Entom., 7th Ed., p. 458. 132 EVENINGS AT THE MICROSCOPE. a minute fleshy bulb. Those from the areas near and at the margins of the palms more and more arch out- wards, so that the space covered by the bulbs of the filaments is considerably greater than that of the paln itself, Now it is evident that the bulbous extremities of these soft filaments are the organs of adhesion. We notice how they drag and hold, as the fly draws its foot from its place, and it seems almost certain that the ad- hesion is effected by means of a glutinous secretion poured out in minute quantities from these fleshy tips. When the foot is suddenly removed, we may often see a number of tiny particles of fluid left on the glass where the filaments had been in con- tact with it: but I do not build conclusively on this ap- pearance, because the fly, having been confined for some quarter of an hour in this nearly tight glass cell, has doubtless exhaled some moisture, which has condens- ed on the glass; and the specks we see may possibly be due to the filaments of the palms having become wet by repeat- edly brushing the moist sur- face. Mr. Hepworth, how- ever, asserts that a fluid is poured out from these fila- ments, and is deposited on the glass, when the fly is vigorous, with great regularity. Ile says that “when in a partially dormant state, the FOOT OF FLY. INSECTS ! THEIR FEET. 133 insect does not appear to be able to give out this secre- tion, though it can still attach itself: indeed, this fluid is not essential for that purpose.”* It is asserted that the speckled pattern of fluid left on the glass by the fly’s footsteps remains (if breathed on) when the moisture is evaporated ; and hence it is presumed to be of an oily nature. In some Beetles the joints of the foot are furnished with similar appendages. I shall now show you the fore-foot of a well-known insect, called by children the Bloody-nose Beetle (Timarcha tenebricosa), a heavy- bodied fellow, of a blue-black colour, abundant in spring and summer on hedge-banks. You have doubt- less often observed it, and have been amused, perhaps, at seeing the drop of clear scarlet fluid which exudes from its mouth when touched. The feet in this species are broad and well devel- oped. You may see with the naked eye, on turning it up, that its dilated joints are covered on the under surface with a velvety cushion of a rusty-brown colour ; and here, under a low power of the microscope with the Lieberkuhn, you can resolve the nature of the velvet. The foot, or tarsus as it is technically called, is com- posed of four very distinct pieces ; of which the first is semicircular, the second crescent-shaped, the third heart-shaped, and the fourth nearly oval. The last is rounded on all sides, has no cushioned sole, and carries two stout hooks. The first three are flat or even, hol- lowed beneath into soles, something like the hoof of a horse, and the whole interior bristles with close-set minute points, the tips of which terminate at the same * Microse. Journal, for April, 1854. 154 EVENINGS AT THE MICROSCOPE. level and form a velvety surface. Now these points are the whitish bulbous extremitics exactly answerable to those of the palms of the fly, and doubtless they answer the very same purpose. Only here they are set in far closer array and are a hundred times more numerous ; whence we may reasonabiy presume a higher power of adhesion to be possessed by the beetle. The structure is best seen in the male, which may be distinguished by its smaller dimensions, and by its broader feet. A still better example of a sucking foot is this of the FOOT OF WATER-BEETLE. 2. One of the last more enlarged. a. Large sucker. 0b. Two smaller suckers. c. Small crowded suckers. Dyticus marginalis. It isthe great flat oval beetle, which is fond of coming up to the surface of ponds, and hanging there by the tail with its pair of hind legs INSECTS : THEIR FEET. 135 stuck out on each side at right angles; the redoubt- able monster which little boys who bathe hold in such salutary awe under the name of Toe-biter. We have turned the tables upon the warrior, and have bitten /zs toe—off, and here it is. This is the tarsus of one of the fore limbs. The peculiarity that first strikes us is that the first three joints are as it were fused into one, and dilated so as to make a large roundish plate. The under surface of this broad plate is covered with a remarkable array of sucking disks, of which one is very large, occupying about a fourth part of the whole area. It is circular, and its face is strongly marked with numerous fibres radiating from the centre. Near this you perceive two others of similar form and structure, but not more than one tenth part of its size; one of these, moreover, is smaller than the other. Indeed, the size and number _of these organs differ in different individuals of the same species. The greater number of the suckers are comparatively minute ; but they are proportionally multitudinous and crowded. Each consists of a club-shaped shaft, with a circular disk of radiating fibres attached to its end. The whole apparatus constitutes a very effective instru- ment of adhesion. There is a somewhat similar dilatation of the first joints of the tarsus, but for a very different object, in the Honey-bee; and it is particularly worthy to be ob- served, not only for the interesting part which it plays in the economy of the insect, but for the example it af- fords us of the adaptation of one and the same organ to widely different vses, by a slight modification of its structure. 136 EVENINGS AT THE MICROSCOPE. It is the hind foot of the Bee that we are now to ex- amine. The first joint is, as you see, enlarged into a wide, long, and somewhat ovate form, constituting a flattish plate, slightly convex on both surfaces. The upper face presents nothing remarkable, but the under side is set with about nine stiff combs, the teeth of which are horny straight spines, set in close array, and arranged in transverse rows across the joint, nearly on a level with its plane, but a little projecting, and so ordered that the tips of one comb slightly overlap the bases of the next. We see them in this example very distinct, because their colour, a clear reddish-brown, contrasts with a multitude of tiny globules of a pale yellow hue, like minute eggs, which are entangled in the combs. Now these globules serve to illustrate the object of this apparatus. They are grains of pollen; the dust that is discharged from the anthers of flowers, which being kneaded up with honey forms the food of the in- fant bees, and is, therefore, collected with great perse- verance by those industrious insects; and the way in which they collect it is, by raking or combing it from the anthers, by means of these effective instruments on their hind feet. You see that in this specimen the combs are loaded with the grains, which lie thickly in the furrows be- tween one comb and another. But how do they dis- charge their gatherings? Do they return to the hive, as soon as they have accumulated a quantity such as this, which one would suppose they could gather in two or three scrapes of the foot? No; they carry a pair of panniers, or collecting baskets, which they grad- INSECTS : THEIR FEET. 137 ually fill from the combs, and then return to deposit the results of their collecting. One of these baskets I can show you; and, indeed, we should be unpardonable to overlook it, for it is the companion structure to the former. JI make the stage forceps to revolve on it axis, and thus bring into focus the joint (¢/bia) immediately above that of the combs, and so that we shall look at its opposite sur- face; that is, the outer. We notice at once two or three peculiarities, which distinguish the joint in this instance from other parts of the same limb, and*from the corresponding part in the same limb of other insects. First, the surface is decidedly concave, whereas it is ordinarily convex. Secondly, this concave surface is smooth and polished (except that it is covered with a minute network of crossed lines), not a single hair, even the most minute, can be discerned in any part; whereas the corresponding surface of the next joints, both above and below, is studded with fine hairs, as is the exterior of insects generally. Thirdly, the edges of this hollowed basin are beset with long, slender, acute spines, which pursue the same curve as the bottom and sides, expanding widely, and arching up- ward. Here, then, we have a capital collecting-basket. Its coneavity of course fits it to contain the pollen. Then its freedom from hairs is important: hairs would be out of place in the concavity. Thirdly, the mar- ginal spines greatly increase the capacity of the vessel to receive the load, on the principle of the sloping stakes which the farmer plants along the sides of his waggon when he is going to carry a load of hay o1 corn. [38 EVENINGS AT THE MICROSCOPE. But, you ask, how can the Bee manage to transfer the pollen from the combs to the basket ? Can she bend up the tarsus to the tibia? or, if she can, surely she could only reach the inner, not the outer surface of the latter. How is this managed / A very shrewd question. Truth to say, the basket you have been looking at never received a single grain from the combs of the joint below it. But the Bee has a pair of baskets and @ pazr of comb-joints. It is the right set of combs that fills the left basket, and vice versd. She can easily cross her hind-legs, and thus bring the tarsus of one into contact with the tibia of the other ; and if you will pay a moment’s more attention to the matter, you will discover some further points of interest in this beautiful series of contrivances still. If you look at this living bee, you notice that, from the position of the joints, when the insect would bring one hind-foot across to the other, the under surface of the tarsus would naturally scrape the edge of the opposite tibia in a direction from the bases of the combs to- wards their tips ; and, further, that the edge of the tibia so scraped would be the Aznder edge, as the leg is or- dinarily carried in the act of walking. Now, if you take another glance at the basket-joint in the forceps of the microscope, you will see—what, perhaps, you have already noticed—that the marginal spines have not exactly the same curvature on the two opposite edges, but that those of the one edge are nearly straight, or at most but slightly bowed, whereas those of the opposite edge are strongly curved, the are in many of them reaching even to a semicircle, so that their points, after performing the outward arch, return to a position perpendicularly over the medial line of the basket. INSECTS : THEIR FEET. 139 It is the outer or hinder edge of the joint that carries the comparatively straight spines. These receive the grains from the combs, which, then falling into the basket, are received into the wide concavity formed partly by its bottom and sides, but principally by the arching spines of the opposite edge. ‘Their curving form would have been less suitable than the straighter one to pass through the interstices of the combs, because it would be much more difficult to get at their points ; while, on the other hand, the straight lines of these would have been far less effective as a receiver for the burden. The thickness of the spines is just that which enables them to pass freely through the interstices of the comb-teeth, and no more. On the whole, this combination of contrivances reads us as instructive a lesson of the wisdom of God dis- played in creation as any that we have had brought under our observation. The end to be attained by all this apparatus is worthy of the wondrous skill displayed in its coutri- vance ; for it is connected with the feeding of the stock, and whatever diminishes the labour of the individual bees enables a larger number to be supported. But valuable as is the Honey-bee to man, there are other important purposes to be accomplished, which are more or less dependent, collaterally, on this series of contri- vances. “In many instances it is only by the bees travelling from flower to flower that the pollen and farina is ecar- ried from the male to the female flowers, without which they could not fructify. One species of bee would not be sufficient to fructify all the various sorts of flowers, were ‘he bees of that species ever so numer- 140 EVENINGS AT THE MICROSCOPE. ous; for it requires species of different sizes and differ- ent constructions. M. Sprengel found that not only are insects indispensable in fructifying different species of Jris, but some of them, as Z. Xiphiwm, require the agency of the larger humble-bees, which alone are strong enough to force their way beneath the style-flag ; and hence, as these insects are not so common as many others, this /rzs is often barren, or bears imperfect seeds.” * The legs and feet of Caterpillars are constructed on a very different plan from those of perfect insects, as you may see in this living Silkworm. The first three segments of the body, reckoning from the head, are furnished each with a pair of short curved limbs set close together on the under side. These represent the true legs of the future moth, and show, notwithstanding their shortness, four distinct joints, of which the last is a little pointed horny claw. The whole limb resembles a short stout hook. The two segments occur which are quite smooth beneath, and destitute of limbs; and then on the sixth we begin to find another series, which goes on regularly, a pair on each segment, to the eleventh and final one, with the single exception of the tenth segment, which is again deprived of limbs. But these organs are of a very peculiar character. They have no representatives in the mature insect, but disappear with the larva state, and they are not con- sidered limbs-proper at all, but mere accessory develop- ments of the skin to serve a special purpose. They are sometimes called claspers, sometimes false-legs, but more commonly pro-legs. Each consists of a fleshy wart, which is zapable te * Penny Cyclop., art. BEE. INSECTS : THEIR FEET. 141 soine extent of being turned inside out, like the finger of aglove. Partly around the blunt and truncate ex- tremity are set two rows of minute hooks, occupying the side next the middle line of the caterpillar in a semi- circle along the margin. These hooks arch outward as regards the axis of the pro-leg, though the majority of them point towards the medial line of the body. The double row is somewhat interrupted at its middle point ; and just there, in each pro-leg, a clear vesicle or fleshy bladder protrudes from the sole, which may perhaps serve as a very delicate organ of touch, or may exude a viscid secretion helpful to progress on smooth bodies. The hooks seem adapted to catch and hold the fine threads of silk, which most caterpillars spin as a carpet for their steps. In some eases the circle of hooks is complete, as in this example, which I find in one of the slides of my ‘drawer, marked “ Pro-leg of a Caterpillar.” It is some Jarge species, probably a Sphinx, fer the hooks are very large, of a clear orange-brown hue, and set in a long oval ring—single as to their bases, but double as to their points—completely around the extremity of the foot. These hooks are simply cutaneous, as may be well seen in this prepared specimen,—doubt- less mounted in Canada balsam ;—for their origins are mere blunt points, set most superficially in the thin skin without any enlargement or apparent bulb. 142 EVENINGS AT THE MICROSCOPE. CHAPTER VII. INSECTS } STINGS AND OVIPOSITORS. Propasiy at some period of your life you have been stung by a bee or wasp. I shall take it for granted that you have, and that having tested the potency of these warlike insects’ weapons with one sense, you have a curiosity to examine them with another. The micro- scope shail aid your vision to investigate the morbifie implement. This is the sting of the Honey-bee, which I have but this moment extracted. It consists of a dark brown horny sheath, bulbous at the base, but suddenly dimin- ishing, and then tapering to a fine point. This sheath is split entirely along the inferior edge, and by pressure with a needle I have been enabied to project the two lancets, which commonly lie within the sheath. These are two slender filaments of the like brown horny sub- stance, of which the centre is tubular, and carries a fluid, in which bubbles are visible. The extremity of each displays a beautiful mechanism, for it is thinned away into two thin blade-edges, of which one remains keen and knife-like, while the opposite edge is cut into several saw-teeth pointing backwards. The lancets do not appear to be united with the sheath in any part, but simply to lie in its groove ; their basal portions pass out into the body behind the sheath, where you see a number of muscle-bands crowded INSECTS : STINGS AND OVIPOSITORS. 143 around them: these, acting in various directions, and being inserted into the lancets at various points, exercise a complete control over their movements, projecting or retracting them at their will. But each lancet has a singular projection from its back, which appears to act in some way as a guide to its motion, probably prevent- irg if from slipping aside when darted forth, for the bulbous part of the sheath, in which these projections work, seems formed expressly to receive them. Thus we see an apparatus beautifully contrived to enter the flesh of an enemy : the two spears finely point- ed, sharp-edged, and saw-toothed, adapted for piercing, cutting, and tearing; the reversed direction of the teeth gives the weapon a hold in the flesh, and prevents it from being readily drawn out. Here is an elaborate store of power for the jactation of the javelins, in the numerous muscle-bands; here is a provision made for the precision of the impulse; and finally, here is a pol- ished sheath for the reception of the weapons and their preservation when not in actual use. All this is per- fect ; but something still was wanting to render the weapons effective, and that something your experience has proved to be supplied. The mere intromission of these points, incomparably finer and sharper than the finest needle that was ever polished in a Sheffield workshop, would produce no re- sult appreciable to our feelings ; and most surely would not be followed by the distressing agony attendant on the sting of a bee. We must look for something more than we have seen. We need not be long in finding it. For here, at the base of the sheath, into which it enters by a narrow neck, lies a transparent pear-shaped bag, its surface 144 EVENINGS AT’ THE MICROSCOPE. covered all over, but especially towards the neck, with small glands set transversely. It is rounded behind, STING OF BEF. a. Tip of Lancet, more enlarged. where it is entered by a very long and slender mem- branous tube, which, after many turns and windings, gradually thickening and becoming more evidently glandular, terminates in a blind end. This is the apparatus for preparing and ejecting a powerful poison. The glan- dular end of the slender tube is the secreting organ : here the venom is_ pre- pared; the remainder of the tube is a duct for con- veying it to the bag, a re- servoir in which it is stored for the moment of use. By means of the neck it is thrown into the groove at the moment the sting is projected, the same mus- cles, probably, that dart forward the weapon com- pressing the poison-bag and causing it to pour forth its contents into the groove, whence it passes on be- tween the two spears in‘o the wound which they have made. INSECTS : STINGS AND OVIPOSITORS. 145 A modification of this apparatus is found through. out avery extensive order of insects,—the Wymenop- tera; but in the majority of cases it is not connected with purposes of warfare. Wherever it occurs it is al- ways confined to the female sex, or (as in the case of some social insects) to the neuters, which are undevel- oped females. When it is not accompanied by a poison- reservoir it is ancillary to the deposition of the eggs, and is hence called an ovipositor, though in many cases it performs a part much more extensive than the mere placing of the ova. In the large tribe of Cuckoo-flies Zcehneumonide), which spend their egg and larva states in the living bodies of other insects, this ovipositor is often of great length ; even many times longer than the rest of their bodies; for the larve which have to be pierced by it require to be reached at the bottom of deep holes and other recesses in which the providence of the parent had placed them for security. The structure of the or- gan may be seen in this little species, not more than one-sixth of an inch in entire length, of which the ovi- positor projects about a line. Under the microscope you see that this projection consists of two black fleshy filaments, rounded without and flattened on their inner faces, which are placed together,—and of the true im- plement for boring, in the form of a perfectly straight awl, of a clear amber hue, very slender and brought to an abrupt oblique point, where there are a few exceed- ingly fine reverted teeth. It is probably double, though it refuses to open under the pressure which I bring to bear upon it. Atthe base are seen within the semi- pellucid abdomen the slender horns, on which the mus- cles act in projecting the borer. 146 EVENINGS AT THE MICROSCOPE. You are doubtless aware that the little berries which look like bunches of green currants often seen growing on the oak, are not the proper fruit of the tree, but dis- eased developments produced by a tiny insect, for the protection and support of her young. But perhaps you have never paid any special attention to the living atom whose workmanship they are, and are not familiar with the singular mechanism by which she works. I have not had an opportunity of seeing it myself, and there- fore cannot show it to you; but as Gall-flies are by no means rare, and you may easily rear a brood of flies from the galls, you may have a chance of meeting with it. I will therefore quote to you what Rennie says about it. “There can be no doubt, that the mother gall-fly makes a hole in the plant for the purpose of depositing her eggs. She is furnished with an admirable oviposi- tor for that express purpose, and Swammerdam actually saw a gall-fly thus depositing her eggs, and we have recently witnessed the same in several instances. In GALL-FLY AND MECHANISM OF OVIPOSITOR. some of these insects the ovipositor is conspicuously long, even when the insect is at rest ; but in others, not above a line or two of it is visible, till the belly of the INSECTS : STINGS AND OVIPOSITORS. 147 insect be gently pressed. When this is done to the fly that produces the currant-gall of the oak, the ovipositor may be seen issuing from a sheath in form of a small curved needle, of a chesnut-brown colour, and of a horny substance, and three times as long as it at first appeared. “ What is most remarkable in this ovipositor is, that it is much longer than the whole body of the in- sect, in whose belly it is lodged in a sheath, and, from its horny nature, it cannot be either shortened or length- ened. It ison this account that it is bent into the same eurve as the body of the insect. The mechanism by which this is effected is similar to that of the tongue of the woodpeckers (Picide), which, though rather short, ean be darted out far beyond the beak by means of a forked bone at the root of the tongue, which is thin and rolled up like the spring of a watch. The base of the ovipositor of the gall-fly is, in a similar way, placed near the anus, runs along the curvature of the back, makes a turn at the breast, and then, following the curve of the belly, appears again near where it originates. “ With. this instrument the mother gall-fly pierces the part of a plant which she selects, and, according to our older naturalists, ‘ejects into the cavity a drop of her corroding liquor, and immediately lays an ege or more there ; the circulation of the sap being thus inter- rupted, and thrown, by the poison, into a fermentation that burns the contiguous parts and changes the na- tural colour. The sap, turned from its proper channel, extravasates and flows round the eggs, while its surface is dried by the external air, and hardens into a vaulted form.’ Kirby and Spence tell us, that the parent-fly 148 EVENINGS AT THE MICROSCOPE. introduces her egg ‘into a puncture made by her eu- rious spiral sting, and in a few hours it becomes sur- rounded with a fleshy chamber. M. Virey says, the gall-tubercle is produced by irritation, in the same way as an inflamed tumour in an animal body, by the swell- ing of the cellular tissue, and the flow of liquid matter, which changes the organization, and alters the natural external form.” * Perhaps a still more charming example of animal mechanics is that furnished to us by the Saw-flies (Zew- thredinide). ‘These are very common four-winged insects of rather small size, many species of which are found in gardens and along hedges, in summer, pro- duced from grubs which are often mistaken for true caterpillars, as they strip our gooseberry and rose bushes of their leaves; but may be distinguished from them by the number of their pro-legs, and by their sin- gular postures; for they possess from eight to four- teen pairs of the former organs, and have the habit of coiling up the hinder part of their body in a spiral ring, while they hang on to the leaf by their six true feet. These saw-fly caterpillars are produced from eggs which are deposited in grooves, made by the parent-fly in the bark of the tree or shrub whose future leaves are destined to constitute their food; and it is for the construction of these grooves and the deposition of the egos in them, that the curious mechanism is contrived which I am now bringing under your notice. Almost all our acquaintance with this instrnment and the manner of its employment, we owe to the em- inent French naturalist Réaumur, and to his Italian * Ins. Arch. 671. YNSECTS : STINGS AND OVIPOSITORS. 149 contemporary Valisnieri. Their details I shall first cite, as they have been put into an English dress by Rennie, and then show you a specimen dissected out by myself, and point out some agreements and some discrepancies between it and them. “In order to see the ovipositor, a female saw-fly must be taken, and her belly gently pressed, when a narrow slit will be observed to open at some distance from the anus, and a short, pointed, and somewhat eurved body, of a brown colour and horny substance, will be protruded. The curved plates which form the sides of the slit, are the termination of the sheath, in which the instrument lies concealed till it is wanted by the insect. “The instrument thus brought into view, is a very finely contrived saw, made of horn, and adapted for penetrating branches and other parts of plants where the eggs are to be deposited. The ovipositor-saw of the insect is much more complicated than any of those employed by our carpenters. The teeth of our saws are formed in a line, but in such a manner as to cut in two lines parallel to and at a small distance from each other. This is effected by slightly bending the points of the alternate teeth right and left, so that one half of the whole teeth stand a little to the right, and the other half a little to the left. The distance of the two parallel lines thus formed is called the course of the saw, and it is only the portion of wood which lies in the course that is cut into sawdust by the action of the instru- ment. It will follow, that in proportion to the thin- ness of a saw there will be the less destruction of wood which may be sawed. When cabinet-makers have to divide valuable wood into very thin leaves, they ac- 150 EVENINGS AT THE MICROSCOPE. cordingly employ saws with a narrow course; while sawyers who cut planks, use one with a broad course. The ovipositor-saw being extremely fine, does not re- quire the teeth to diverge much, but from the manner from which they operate, it is requisite that they should not stand like those of our saws in a straight line. The greater portion of the edge of the instrument, on the contrary, is towards the point somewhat concave, sim- ilar to a scythe, while towards the base it becomes a little convex, the whole edge being nearly the shape of an italic f. “The ovipositor-saw of the fly is put in motion in the same way as a carpenter’s hand-saw, supposing the tendons attached to its base to form the handle, and the muscles which put it in motion to be the hand of the carpenter. But the carpenter can only work one saw at a time, whereas each of these flies is furnished with two, equal and similar, which it works at the same time—one being advanced and the other retracted al- ternately. The secret, indeed, of working more saws than one at once is not unknown to our mechanies ; for two or three are. sometimes fixed in the same frame. These, however, not only all move upwards and down- wards simultaneously, but cut the wood in different places; while the two saws of the ovipositor work in the same cut, and, consequently, though the teeth are extremely fine, the effect is similar to [that of] a saw with a wide set. “Tt is important, seeing that the ovipositor-saws are so fine, that they be not bent or separated while in operation—and this, also, nature has provided for by lodging the backs of the saws in a groove, formed by two membranous plates, similar to the structure of INSECTS : STINGS AND OVIPOSITURS. 1 a clasp-knife. These plates are thickest at the base, becoming gradually thinner as they approach the point which the form of the saws requires. According to Valisnieri, it is not the only use of this apparatus to form a back for the saws, he having discovered be- tween the component membranes two canals, which he eupposes are employed to conduct the eggs of the in- sect into the grooves which she has hollowed out for them. “The teeth of a carpenter’s saw, it may be re- marked, are simple, whereas the teeth of the ovipositor- saw are themselves denticulated with fine teeth. The latter, also, combines at the same time the properties of a saw and of a rasp or file. So far as we are aware, these two properties have never been combined in any of the tools of our carpenters. The rasping part of the ovipositor, however, is not constructed like our _rasps, with short teeth thickly studded together, but has teeth almost as long as those of the saw, and placed contiguous to them on the back of the instru- ment, resembling in their form and setting the teeth of a comb.” * Now look at this object which I have just extracted from the abdomen of a rather large female Saw-fly, of a bright green hue, spotted with black. The first por- tion of the apparatus that protruded on pressure, was this pair of saws of an flike figure. These agree in general with those described; here is, in each, the doubly-curved blade, the strengthened back, the rasp- like jagging of the lateral surfaces, the teeth along the edge, and the secondary toothlets of the latter. All these essential elements we see, but there is much dis: * Insect Architecture, 153. 152 EVENINGS AT THE MICROSCOPE. crepancy in the detail, and many points not noticed ;— in part, doubtless, owing to its being another species which was under observation, and partly to the infe- riority of the microscopes employed a hundred and fifty years ago, to those we are using. In the first place the curve of the 7 is different, the convexity of the edge being towards the point and the concavity nearest the base. Then the strengthening does not appear to me a groove in which the saw plays, but a thickening of the substance of the back. Each main tooth of the saw in this case is the central point in the edge of square plate, which appears to be slightly concave on its two surfaces, being thickened at its two sides, at each of which, where it is united to the follow- ing plate, it rises and forms with it a prominent ridge running transverse to the course of the saw. Each of these ridges then forms a second tooth, as stout as the main edge-tooth, which, with the rest of the same series, forms a row of teeth on the oblique side of the saw, in a very peculiar manner, difficult to express by words. It is singular that this side of the saw should be studded with minute hairs, since these would seem to interfere with the action of the saw, or at least be liable to be themselves rubbed down and destroyed in its action. But their existence is indubitable; there they are, pointing at a very acute angle towards the top of the saw. The back edge of the implement bristles with many close-set hairs or spines, forming a sort of brush, but pointing in the opposite direction. Each main tooth of the edge-series is cut into one or two minute toothlets on its posterior side (next the base of the saw) and about half-a-dozen on its opposite side (next the tip). The texture is clear and colourless INSECTS } STINGS AND OVIPOSITORS. 153 where thin; but in the thickened parts, as the main teeth, the transverse ridges, and the back, it is a clear amber-yellow ; the strengthening back-piece deepening to a rich translucent brown. There is, however, in this species of mine a second set of implements of which the French naturalist, ob- OUTER SAW OF SAW-FLY. a. A portion more enlarged. servant as he was, takes not the slightest notice; and his English commentator appears to have as little sus- pected its presence. This pair of saws that we have been looking at is but the sheath of a still finer pair of laneets or saws, which you may see here. These are much slenderer than the former, and are peculiar in their construction. Their extreme tip only bears saw- teeth, and these are directed backwards, but one side of the entire length presents a succession of cutting edges, as if a number of short pieces of knife-blades had been cemented on a rod, in such a manner as that the cutting edges should be directed backwards, and over- lap each other. The other lateral surface is plain, and both are convex in their general aspect. The appear- nce of these implements is very beautiful; for the 7* 154 EVENINGS AT THE MICROSCOPE. texture is of a clear pale amber, but the structure is strengthened by a band which runs along each edge, and by transverse bands crossing at regular intervals, of a denser tissue ; and these are of a rich golden trans- lucent brown. From the construction of this implement I should infer that its force is exerted in pulling and not in push- ing; the direction of the teeth and of the cutting plates INNER SAW OF SAW-FLY. shows this. The sharp horny point is probably thrust a little way into the solid wood or bark, and then a backward pull brings the teeth and cutting plates to act upon the material, and so successively. And prob- ably these points are the first parts of the whole ap- paratus that come into operation; the blunter saw of the sheath serving mainly to widen and deepen the course, after the finer points have pioneered the way. You may like to hear what Réaumur has to say about the manner in which the fly works, especially as I have nothing of my own on the subject, which yet is a most interesting one :— “When a female Saw-fly has selected the branch of a rose-tree, or any other, in which to deposit her eggs, she may be seen bending the end of her belly inwards. in form of a crescent, and protruding her saw, at the INSECTS ! STINGS AND OVIPOSITORS. 155 same time, to penetrate the bark or wood. She main- tains this recurved position so long as she works in deepening the groove; but when she has attained the depth required, she unbends her body into a straight line, and in this position works upon the place length- ways, by applying the saw more horizontally. When she has rendered the groove as large as she wishes, the motion of the tendon ceases, and an egg is placed in the cavity. The saw is then withdrawn into the sheath for about two-thirds of its length, and at the same mo- ment, a sort of frothy liquid, similar to a lather made with soap, is dropped over the egg, either for the pur- pose of gluing it in its place, or sheathing it from the action of the juices of the tree. She proceeds in the same manner in sawing out a second groove, and so on in succession, till she has deposited all her eggs, some- times to the number of twenty-four. The grooves are usually placed in a line, at a small distance from one another, on the same branch; but sometimes the mother-fly shifts to another, or to a different part of the branch, when she is either scared or finds it unsuitable. She commonly, also, takes more than one day to the work, notwithstanding the superiority of her tools. Réaumur has seen a Saw-fly make six grooves in suc- cession, which occupied her about ten hours and a- half, “The grooves, when finished, have externally little elevation above the level of the bark, appearing like the puncture of a lancet in the human skin; but in the course of a day or two the part becomes first brown and then black, while it also becomes more and more elevated. This increased elevation is not owing to the growth of the bark, the fibres of which, indeed, have 156 EVENINGS AT THE MICROSCOPE. been destroyed by the ovipositor-saw, but to the actual growth of the egg; for, when a new-laid egg of the Saw-fly is compared with one which has been several days inclosed in the groove, the latter will be found to be very considerably larger. This growth of the egg is contrary to the analogy observable in the eggs of birds, and even of most other insects; but it has its advan- tages. As it continues to increase, it raises the bark more and more, and consequently widens, at the same time, the slit at the entrance ; so that, when the grub is hatched, it finds a passage ready for its exit. The mother-fly seems to be aware of this growth of her eggs, for she takes care to deposit them at such distances as may prevent their disturbing one another by their development.” * The merry little jumping insects called Frog-hop- pers (Zettigonia), one of which in its larva state emits the little mass of froth so common on shrubs, and called cuckoo-spit, are furnished with a set of tools for thei own private carpentry, which, though less elaborate than those of the saw-flies, are worthy of a moment’s glance. If we catch one of these vaulters and gently press the abdomen, we shall see proceeding from its hinder and lower part, a thickish piece, large com- pared with the size of the insect, which it is then easy to extract with a pair of fine pointed pliers. 1 have just done this, and here is the result on a slip of glass. First there is a pair of brown protecting pieces, ok long in form, and studded with hairs like the rest ot the.exterior of the body. From between them" projects what resembles a lancet, of the usual translucent amber. * Insect Architecture, 155. — INSECTS : STINGS AND OVIPOSITORS. 157 coloured horn, appropriated to these instruments (which is to them what steel is to us); and which we shall presently discover to be composed of two blades exactly alike, convex without and concave within, applied face to face. One edge of this pair of implements is quite smooth, but the other is cut into the most beautifully regular and most minute teeth. This, however, is but the sheath. Within the two spoon-shaped faces there le two other lancets, blade to blade, still finer and more delicate. Both edges of these blades are of the most perfect keenness, without a flaw ; but their sides appear roughened with rows of very minute horny knobs, lie a rasp. I shall illustrate this demonstration by another ex- tract from Réaumur, premising, however, that his ob- servations refer to the large species of true Cicade from warmer latitudes, whose machinery seems to differ from that of our little friends in some particulars. For example, the two inner lancets seem to be united in one, in Réaumur’s species, or else, which I think more probable, he did not succeed in separating them. He describes the two curved spoon-shaped pieces, as finely indented on both sides with teeth ; which are strong, nine in number, arranged with great symmetry, increasing in fineness towards the point. This instru- ment he describes as composed of three pieces, the two exterior, which he calls the ji/es, and another pointed, which he compares to a lancet, which is not toothed. “The files are capable of being moved forward and backward, while the centre one remains stationary ; and as this motion is effected by pressing a pin or the blade of a knife over the muscles on either side at the 158 — EVENINGS AT THE MICROSCOPE. origin of the ovipositor, it may be presumed that those muscles are destined for producing similar movements when the insect requires them. By means of a finely- pointed pin carefully introduced between the pieces, and pushed very gently downwards, they may be, with no great difficulty, separated in their whole ex- tent. “The contrivances by which those three pieces are held united, while at the same time the two files can be easily put in motion, are similar to some of our own mechanical inventions, with this difference, that no hu- man workman could construct an instrument of this description so small, fine, exquisitely polished, and fit- ting so exactly. We should have been apt to form the grooves in the central piece, whereas they are scooped out in the handles of, the files, and play upon two pro- jecting ridges in the central piece, by which means this is rendered stronger. M. Réaumur discovered that the best manner of showing the play of this extraordinary instrument is to cut it off with a pair of scissors near its origin, and then, taking it between the thumb and the finger at the point of section, work it gently to put the files in motion. “ Beside the. muscles necessary for the movement of the files, the handle of each is terminated by a curve of the same hard horny substance as itself, which not only furnishes the muscles with a sort of lever, but serves to press, as with a spring, the two files close to the central piece.” * The use of these instruments is the same as I have already alluded to in the case of the saw-flies. The female Tree-hopper deposits her eggs in holes which she * Insect Architecture, 149. INSECTS ! STINGS AND OVIPOSITORS. 159 bores in dead twigs by means of these files and lancets. The branches chosen are said to be recognisable by being studded with little oblong elevations, caused by the partial raising of a splinter of wood at the orifice of the hole, to which it serves as a cover. These are arranged in a single line, the holes which they protect being only half-an-inch in length, and reaching to the pith, whose course they then follow. Not more than six or eight eggs are laid in each hole, but an idea of the labours of the industrious and provident mcther will be formed from the fact that each lays six or seven hundred eggs in the course of the sum- mer. 160 EVENINGS AT THE MICROSCOPE. CHAPTER IX. INSECTS : THEIR MOUTHS. Tue parts of the mouth in different insects afford an almost endless store of delightful observations ; and the more as, with all their variety, they are found to be in every case composed of the same essential elements. You would not think so, indeed ; you would naturally suppose—looking at the biting jaws of a Beetle, the piercing proboscis of a Bug, the long elegantly-coiled sucker of a Butterfly, the licking tongue of a Bee, the cutting lancets of a Horse-fly, and the stinging tube of a Gnat—that each of these organs was composed on a plan of its own, and that no common structure could exist in instruments so diverse. But it is so, as we shall see. We may consider the various organs of the mouth as most harmoniously and perfectly developed in the active carnivorous Beetles, the Carabidae, or ground- beetles, for instance. Let us examine the head of this black Scarites, from the garden; and first from above. In front of the polished head-shield, and jointed to it by a broad transverse straight edge, is a four-sided piece, forming an oblong square, nearly twice as broad as long, a little convex, and marked with six little p*ts INSECTS : THEIR MOUTIIS. 161 or sinkings of the surface, along its front edge. This is the upper lip ; but, instead of being fleshy, as ours is, it is composed of a hard polished black shelly substance, of a peculiar nature, called chitine, the same substance as the hard parts of all Insects and Crustacea are made of. From beneath the sides of this there project on each side two broad hooked pieces, which, as you see, I can with a needle force out laterally, so as to show their form better, for they hinge upon the sides of the face, beneath the heads-hield. Each forms the half of a cres- cent, the curved points of which are turned towards each other, and can work upon each other, the points crossing, like shears. These are the proper biting jaws, or mandibles, and in many of the larger beetles they have great power of holding and crushing. Some- times, their inner side is cut into strong teeth, but here . this side forms a blunt cutting edge; the upper surface, however, is scored with ridges and furrows, like a file, and this structure is best seen in the left jaw, which, when the pair close, crosses over the right. This is an action of the jaws the reverse of ours, but it is char- acteristic of all the articulate classes of animals, ip which the jaws, whenever present, always work hori- zontally, from right to left, and not vertically, up and down. I will now, by making the forceps revolve, bring the under side of the head into view; for without sep- arating the parts by dissection (which, however, is by no means diflicult,) it is impossible to see them all from one point of view. The part nearest our eye now is the chin, a wide horny piece, like the upper lip, jointed to the head by its straight hind edge, but, unlike it, 162 EVENINGS AT THE MICROSCOPE. having its front edge hollowed out with two deep notches, the central piece between them itself notched at its tip. Immediately above this notched central tooth (I speak of the relative position of the parts, sup- posing the insect to be crawling on the ground, without reference to the way in which we turn it about on the microscope), and united with it, there is a sort of solid square pedestal, on which stand a pair of jointed or- gans, and between them an oblong horny plate rounded MOUTH OF BEETLE, (Seen from beneath.) a, upper lip; d, mandibles; c, maxille; @, maxillary palpi; ¢, tongue; jf labial palpi; g, chin. at the tip, where it bears two bristles. This latter is the tongue; while the jointed organs on each side are called feeclers,—palpi ; though this is a begging of the question, for we do not really know the function of these organs. The chin, the tongue (égula), and these palpi, constitute together the under lip. INSECTS : THEIR MOUTHS. 163 Between the tongue and the biting jaws, or man- dibles, we sce a pair of organs similar to these latter, but smaller, less solid and more curved. ‘These are the under or secondary jaws, maxill@, the use of which is to hold the food, while the biting jaws work on it, and to convey it when masticated to the back of the mouth. Their whole inner edge is set with short stiff bristles, which towards the tips of the jaws become spines. Near the base of these jaws, on the outer edge, are jointed two pairs more of palpi, one pair to each jaw ; of which the exterior is much stouter and longer than the interior. Thus this beetle has three pairs of these many-jointed organs, the labial, and the two pairs of maxillary palpi. Now, in this form of mouth, which has been called a perfect or complete mouth—that is, one in which all the constituent parts can be well made out, we find the following organs :—1. the upper lip (labrum) ; 2. the mandibles ; 3. the mawxille ; with a. the maz- illary palpi; 4. the lower lip (abéwm), comprising B. the tongue, x. the labial palpi, 6. the chin (men- tun. I now exhibit to you the head of the Honey-bee The front is occupied by an upper lip, and a pair of biting jaws (mandibles), which do not greatly differ from the same parts ina beetle. The jaws, however, are more hatchet-shaped, or rather like the hoof of a horse, supposing the soles to be the opposing surfaces. The other organs are greatly modified, so that you would scarcely recognise them. The under jaws (maz- ill@) are greatly lengthened, and the two, when placed | in contact, form a kind of imperfect tube, or sheath. Within these is the lower lip, divided into its constit. 164 EVENINGS AT THE MICROSCOPE. uent parts :—the thick opaque chin, at its basal end; then the two labial palpi, each consisting of four joints, of which the two terminal ones are minute, while the two basal are large and greatly lengthened so as to resemble in appearance the mawzlle@, whose function they imitate also; for the pair of palpi when closed JAWS OF BEE, form an inner sheath for the tongue (Zigula). Finally you see this organ, which is the most curiously devel- oped and modified of all; for it is drawn out to a long INSECTS: THEIR MOUTHS. 165 slender cylindrical tube, formed of a multitude of close- set rings, and covered with fine hairs. Some deny it to be tubular, and maintain that it is solid; but certainly it appears to me to have a distinct cavity throughout, with thickish walls. Under a high power the structure of the investing hairs is very interesting; for they are seen to be flat filaments of the yellow chitine, very much dilated at their bases, and set side by side in regular whorls, the bottom edges of which form the rings of which the tongue is composed. The tip is probably a sensitive organ of taste, for it terminates in a minute globose pulpy body, whose surface is beset with tiny curved points. Thus I have pointed out to you all the parts which enter into the mouth of the beetle, except the maxillary palpi; and those, very small indeed, but quite distinct, you may see, on the outer edge of the maxille, just below the point where their outline begins to swell into its graceful curve. The cylindrical tongue is capable of considerable extension and contraction at the will of the animal, being sometimes pushed far out of the mouth, and ai others quite concealed within its sheath. ‘The man- ner,” observes Mr. Newport, “in which the honey is obtained, when the organ is plunged into it at the bot- tom of a flower, is by lapping, or a constant succession of short and quick extensions and contractions of the organ, which occasion the fluid to accumulate upon it, and to ascend along its upper surface, until it reaches the orifice of the tube formed by the approximation of the mawille above, and of the labial palpi, and this part of the /igula below.” Well might Swammerdam, when describing this 166 EVENINGS AT THE MICROSCOPE. exquisite structure, humbly exclaim,— I cannot refrain from confessing, to the glory of the Immense and In- comprehensible Architect, that I have but imperfectly described and represented this small organ; for, to re- present it to the life in its full perfection, as truly most perfect it is, far exceeds the utmost efforts of human knowledge.” Here you may see the implement with which the Bug performs its much-dreaded operation of blood- sucking ; for though this is not the head of the Bed- bug, but of one of the winged species that are found so abundantly on plants, and which I have just obtained by beating the hedge at the bottom of my garden,—yet the structure of the mouth is so exactly alike in all the members of this immense family, that one example will serve for all others. ' From the front of the head, which, owing to the manner in which this part is carried, is the lower part, proceeds a fine thread, about four times as long as the head itself, which passes along between the fore legs, close to the body, beneath the breast. It is, however, at the pleasure of the animal, capable of being brought np so as to point directly forward, and even projected in front of the head, and in the same plane as the body ; a fact which once came under my own observation. I found a Plant-bug (Pentatoma) which had plunged this thread-like sucker of his into the body of a caterpillar, and was walking about with his prey, as if it were of no weight at all; carrying it at the end of his sucker, which was held straight out from the head and a little elevated. He fiercely refused to allow the poor victim to be taken away, being doubtless engaged in sucking its vital juices; just as the Bed-abomination victim- INSECTS : THEIR MOUTHS. 167 ises the unfortunates who have to sleep at some village inn. Well, we put this head with its sucker between the plates of the compressorium, upon the microscope-stage. The thread is an organ composed of four lengthened slender joints, beset with scattered bristles, and termin- ating ina point on which are placed a number of ex- cessively minute radiating warts,—probably the seat of some sensation,—perhaps taste. This jointed organ is the under-lip ; it is slit all down one surface, so that it forms an imperfect tube, or furrow, within which lies the real weapon, a wire of far greater tenuity, which by pressure I can force out of its sheath. It is so slender that its average diameter is not more than ;,',,th of an inch, and it ends in the most acute point; yet this is not a single body, but consists of four distinct wires, lying within one another, and representing the maxille _and the mandibles. These can be separated by the in- sect, and will sometimes open when under examination ; but no instrument that I can apply to them is suffi- ciently delicate to effect their separation at my pleas- ure. Just at the very tip, however, under this high power, we can see, by the semi-transparency of the amber-coloured chitine of which the organ is composed, that there is another tip a little shorter, and as it were contained within the other. This inner point is eut along its edges into saw-teeth pointing backward. Such exquisite mechanism is bestowed upon the strue- ture, and such elaborate contrivance is displayed for the comfort of an obscure and obscene insect, by Him who has not disdained to-exercise his skill and wisdom in its creation ! You know the stout flies which are denominated 168 EVENINGS AT THE MICROSCOPE. Horse-flies or Whame-flies (Zabanus), which are so numerous in the latter part of summer flying around horses, and men too, if we intrude upon their domains. They are continually alighting on the objects of their attentions, and though driven away, returning with annoying pertinacity to the attack. You may always recognise them by the brilliant metallic hues—reds, yel- lows, and greens,—with which their large eyes are painted, often in stripes or bands. These are voracious blood-suckers ; and, as might be supposed from their propensities, they are well furnished with lancets for their surgery. Here you may see their case of instru- ments, which are so effective, that Réaumur tells us, that having compelled one to disgorge the blood it had swallowed, the quantity appeared to him greater than the whole body of the insect could have been supposed capable of containing. All the parts here are formed of the common amber- coloured chitine, brilliantly clear and translucent. The upper lip forms a sort of straight sheath, in which all the other parts are lodged when not in use. The man- dibles are narrow lancets ; of which one edge near the tip is beset with reverted saw-teeth, and the opposite edge with excessively sharp points standing out at right angles, while the surface is roughened with lozenge- shaped knobs set in regular rows. Below these are the maxille, which are the principal cutting instruments ; these are shaped like a carving-knife with a broad blade, strengthened at the basal part of the back by a thick ridge, but brought to a double edge near the tip. The back-edge is perfectly fine and smooth, so that the highest powers of the microscope can only just define its outline; while the other edge is notched into teeth INSECTS : THEIR MOUTHS. 169 so delicate, that twelve of them are cut in the length of a ten-thousandth part of an inch; and yet they are quite regular and symmetrical in length, height and form! I know of no structure of the kind which equals this. These teeth are continued throughout the inner edge of the blade from the tip to the base, and are about eight hundred in number; though the length of the entire blacte is only such that upwards of a hundred and fifty of them, if laid end to end, would not reach to the extent of an inch! The office of these wonderful instruments is doubt- less to cut and enlarge the wound within, and thus pro- mote the flow of blood. The whole apparatus is plunged into the flesh of the victim—horse or man ; then the maaillw expand, cutting as they go, and doubt- less working to and fro as well as laterally, so as to saw the minuter blood-vessels. At the same time the man- dibles, with their saw-teeth on one side, and pricking points on the other, work in like manner, but seem to have a wider range. Finally, there is an execedingly delicate piece beneath all, which seems to represent the labium or under lip. In the active and cunning little Flea, that makes his attacks upon us beneath the shelter of the blankets and under cover of night, the piercing and eutting blades are very minute, and have a peculiar armature. They remind me (only in miniature of course) of those formidable flat weapons which we often sce in mu- seums, the restrums of the huge Saw-fishes (Pristis) ; a great plate of bone covered with grey skin, and set along each side with a row of serried teeth. Tere the blades are similar in form, being long straight narrow laminee of transparent chitine, set along each edge with 8 170 EVENINGS AT THE MICROSCOPP. a double row of glassy points, which project from the surface, and are then hooked backwards. These are the mandibles, and they closely fold together, inclosing an- other narrower blade, the upper lip, which has its two edges studded with similar points, but in a single row. In general, as we have seen, the mawxille are the specially armed weapons, the mandibles acting a second- ary part, often serving as mere sheaths—in those insects which pierce other animals with the mouth. But in this case the mandibles are the favoured parts, the maz- ille being developed into broad leaf-shaped convex sheaths, inclosing the mandibles. There are, however, two cutting blades besides,— the labial palpi, which have their upper edge thick, divided into four distinct joints, and set with bristles,— thus retaining the proper palpine character, while their under edge is thinned away to a fine keen blade, in which there is no sign of jointing. Then there are the maxillary palpi, of which the joints are furnished at their tips with tiny projecting warts, doubtless the seats of a delicate perception, and hollowed into a double series of chambers, which are filled with a dark-coloured fluid. All this is very interesting to behold, and is caleu- lated to exalt our ideas of the wonderful and inexhaust ible resources of Omnipotence, as well as to humble us, when we reflect on how little we certainly understand even of what we see. But common as the Flea is, it is rot a matter of course that you will be able to repeat these observations with the first specimen you put on the stage of your microscope. Several favourable con- ditions must combine in order to insure a successful ex- INSECTS: THEIR MOU1HS. 171 amination. You should choose a female Flea, partly because of her greater size, and partly because the pre- datory weapons are better developed, in all these piere- ing and sucking insects, in the females,—true Amazons. Then you will find it needful to amputate the head, in order to get rid of the front legs, the thick thighs of which else impede your sight of the mouth, being pro- jected on each side of it. And this is a delicate opera- tion: it must be performed on a plate of a glass, under a lens, with one of those dissecting needles whose points are ground to a cutting-edge. Next, having served the head, you must place it in a drop of water, between the plates of your compressorium, the graduated pressure of which, by means of the screw, will cause the organs of the mouth to open and expand separately. Tinally, you must have a good instrument, and a high power: less than 600 diameters will not avail to bring out dis- _ tinetly the toothing of the mandibles and labrum ; and even then you will need delicate manipulation and a practised eye. But the object is worthy of the care bestowed upon it. Once more. Let us submit to examination the complex case of instruments wherewith the Guat per- forms her unwelcome yet skilful surgery. I say “ her,” because among the Gnats, as among most of these puncturing insects, it is the females only who attain skill in the phlebotomic art, the males being innocent of any share in it, and being indeed unprovided with the needful implements. Here is a large specimen, resting with elevated hind legs on the ceiling, and now in alarm off with shril! humming flight to the window. I decapitate her with- out compunction, as it is but a fair penalty tor her 172 EVENINGS AT THE MICROSCOPE. murderous deeds; and, as of old the axeman held up “the head of a traitor” to public gaze, so I lay thas head on the glass of the compressorium for your con- templation. And before I apply pressure to the glass-plate, de- vote a moment’s attention to the tout ensemble. First, the head itself is a hemisphere, almost wholly occupied with the two compound eyes, which present the beaunti- ful appearance of a globe of black velvet, studded with gold buttons arranged in lines crossing each other at right angles. The summit of the head, where the two compound eyes unite, bears a sort of rounded pedestal, the area of which forms the sole part of the head not covered by the organs of vision. On this are placed, side by side, the two antennze, springing from rounded bulbous bases; they consist of twelve (exclusive of the basal bulb) cylindrical joints, which are beset on all sides with short arched hairs, but have besides a whorl of radiating long hairs surrounding the bottom of each joint. The effect of this is exceedingly light and ele- gant. Between these projects a long cylinder, which re- presents the lower lip (Zabcwm); it slightly swells to- wards the tip, where it forms a round, nut-like knob, covered with exceedingly minute papillee, and no doubt constituting a highly sensitive organ of touch. For the greatest part of its length it is covered with lined scales, and with short arched hairs, like the antenne, while each side of its base is guarded by a labial palp of three joints. On applying a graduated pressure, slowly increased to actual contact of the plates (or as near an approxi- mation to it as we can effect), we see first that the nut INSECTS : THEIR MOUTUS. 173 like tip of the Zabiwm expands into two concaye leaves, like the bracts of a bud, and displays two pairs of more delicate leaves within them. Then from a groove along the upper side of the dabiwm, spring out several fila- ments of great clasticity and of the most delicate tenu- ity. One pair of these represent the mandibles; they consist each of a very narrow blade with a stronger back like that of a scythe. Their tip is brought to a most acute point, and the edge in immediate proximity to this is cut into about nine teeth pointing backward : the rest of the edge is smooth, but the whole blade is crossed by a multitude of oblique lines of great delicacy, which may be intended to keep the edge con- stantly keen. Next come the maxilla, or lower jaws, horny filaments as long as the fermer, but still more delicate, constituting simple cut- ting lancets, with a back and a keen blade, a little widening at the tip. Besides these there is the tongue, consisting of a central rod which is distinctly tubular, and of a thin blade on each side, fine-edged and drawn to an acute point. And also the labrum or upper lip, an organ having the LANCETS OF FEMALE GNAT. : : re . ee a, labium. d. tongue. same general form, but consti eee ee tuting animperfect tube; atube, %& mavilla. that is to say, from which about a third of the periphery L74 EVENINGS AT THE MICROSCOPE. is cut away, so as to serve as a sheath for the tongue, which ordinarily lies within its concavity. I scarcely know whether this apparatus is not more wonderfully delicate than any we have examined ;— even than that of the Flea. And how effective it is you doubtless well know ; for when the array of lancets is introduced into the flesh, you are aware that a tumour is left, which by its smart, itching, and inflammation, causes much distress, and lasts many hours. This effect is probably produced partly by the deep penetration of the instruments,—for they are fully one-sixth of an inch in length, and they are inserted to their very base,— and partly by the injection of a poisonous fluid, intend- ed, as has been conjecturally suggested, to dilute the blood and make it more readily flow up the capillary tubes. The channel through which this fluid is injected is probably the tongue, which you see to be permeated by a tube containing a fluid; and the same channel may afford ingress to the diluted blood. The dabiwm does not enter the wound. If you have ever had the philosophie patience to watch a gnat while puncturing your hand, you have observed that the knob at the end of the proboscis is applied to the skin, and that then the organ bends with an angle more and more acute, until at length it forms a double line, being folded on itself, so that the base is brought into close proximity to the skin. Meanwhile the lan- cets have all been plunged in, and are now sunk into your flesh to their very bottom, while the dabiwm, which formed merely the sheath for the whole, is bent up upon itself, ready again to assume its straight form, as soon as the disengaged lancets require its protec: tion. INSECTS . THEIR MOUTHS. 175 The tongue of the common Fies (House-fly, Blow- fly, &c.) is an exquisite microscopical object, from its extreme complexity and beauty. You are familiar with the way in which a fly, having alighted close to a drop of tea on the table, applies to it a proboscis with large dilated extremity, and presently licks it all up. You shall now see the curious implement by which this is effected. The broad portion of the object before us, forming its bottom part, bristling with course black hair, is the TONGUE OF BLOW-FLY. front of the head of a Blow-fly. From the midst of this projects a dark brown mass terminating in two points, and inclosing a narrower and darker object with two L76 EVENINGS AT THE MICROSCOPE. long slender roots, dilated at their bases ;—this is the pair of mazxille altered and modified into a kind of sheath for the mandibles. On each side projects an elegant club, bristled with coarse black hair, and coy- ered besides with a coat of very minute hairs; these clubs are the maxillary palpi. But now we come to the terminal part, consisting of a pair of lobes, together forming a rounded triangle in their outline. This is the dilated and thickened ter- mination of the dabvwm, and is the instrument by which the liquids are so rapidly sucked up. It is impossible to describe this beautiful structure intelligibly: and indeed it is not well understood even by those who have devoted their lives to this branch of natural science. ‘The principal feature apparent is a wide clear membrane, through which run with admirable sym- metry a series of tubes. These tubes consist of four primary ones, all originating near the centre of the ex- pansion, and radiating thence, two backward towards the two lateral angles of the triangle, and the other two nearly side by side towards its point. From each of these, along its outer side only, branch off the minor tubes, very numerous and close together, going off in a slightly sinuous line direct to the margin, diminishing regularly in their course, and at their extremities curv- ing over, so as to bring their open tips to the surface of the skin. The construction of these tubes is highly interest- ing: they are formed, like the air-pipes (trachee), of a multitude of horny rings; but with this peculiarity, that the rings do not form a continuous spiral, but are separate and distinct; and are moreover imperfect ; for each wire (so to speak) does not perform a complete INSECTS : THEIR MOUTHS. 17; circle, but only about two-thirds of a circle, leaving a blank space ; and the tips of the wires end alternately in a fine acute point, and in a rounded fork, like the prongs of a pitch-fork. It has been said that these tubes are modified trachew ; but this fact is by no means obvious to me; for so far from their being con- rected with the general tracheal system, each of the four main tubes originates in an open centre, and each with an open extremity. I think it likely that they are so many suctorial pipes, through which the fluid to be drunk is pumped up, entering at their minute open tips, and discharging itself into the central cavity, by the open basal extremities of the main tubes. The most extraordinary modification of jaws, how- ever, is the long spiral tube which is ordinarily coiled up under the face of a Butterfly or Moth, with which it pumps up the sweet nectar of flowers. Many flow: ers have a deep corolla, and most have the bases of their petals, where the nectar lies, so far from the level of the surface, that probing is necessary to reach it. Bees can enter tubular flowers, and lick their bottoms ; and even blossoms that are closed, as the Snapdragon, they know how to force and enter. But Butterflies, with their wide wings, incapable of being folded, can- not enter flowers bodily, and therefore a peculiar ap- paratus is given them for robbing their contents, as it were, at the doors. Nothing is easier than to examine this beautiful or- gan with the naked eye; and much may be learned of its structure by means of a pocket lens. You may thus sce in a moment, that it forms a flat spiral of several oils, like the mainspring of a watch; that it runs off to a point, and that this point is double, for it is fre g* 178 EVENINGS AT THE MICROSCOPE. quently seen separate a considerable way up. Hence you would probably infer that the organ consists of two equal and consimilar halves, united longitudinally. And so, indeed, it does; and these halves are the rep- resentatives of the maxzlle or lower jaws of the Beetle, being thus greatly developed at the expense of almost all the other parts. The upper lip and the mandibles are discernible only in the form of three most minute plates; the labial palpi are large and prominent,— those well-haired points that project in front of the head, one on each side of the spire. This spiral form of the mawille is called antlia. It is not, however, very easy to fix it in an extended condition on a slip of glass, so as that it shall lie flat throughout its whole length, without injuring the parts or so agglutinating them together, that their structure is concealed or distorted, and in either case unfitted for microscopical examination. The specimen which I have prepared, from the mouth of the Small Garden White - Butterfly, is stretched, and fixed in balsam, and will f think show you the structure under a high power very well. Before we examine it, however, I will.cite you the description of one of the most eminent of microscopical anatomists, Mr. Newport. He considers each mawilla to be composed of an immense number of short trans- verse muscular rings, which are convex externally and concave internally, the two connected organs forming a tube. Within each there are one or more large ¢trachee connected with the trachew in the head. The inner or concave surface which forms the tube is lined with a very smooth membrane, and extends along the anterior margin throughout the whole length of the organ. At INSECTS : THEIR MOUTHS. 179 its commencement at the apex, it occupies nearly the whole breadth of the organ, and is smaller than at its termination near the mouth, where the concavity or groove does not occupy more than about one-third of the breadth. In some species, the extremity of each maxilla is furnished along its anterior and lateral mar- gin with a great number of minute papille. These, in Vanessa Atalanta (the Red Admiral Butterfly) for in- stance, form little barrel-shaped bodies, furnished at the free end with three or more marginal teeth, and a larger pointed body in the centre. There are seventy-four of these in each mazilla, or half the proboscis. Mr. New- port regards them as probably organs of taste. There are also some curious appendages arranged along the inner anterior margin of each mazilla, in the form of minute hooks, which, when the proboscis is extended, serve to unite the two halves together, by the points of _ the hooks in one half being inserted into little depres- sions between the teeth of the opposite side; sometimes these are furnished with a tooth below their tips. With all deference for so respectable an authority, [ cannot help seeing that such is not the structure of the antlia before us. It is evident to me that each half tube is composed of a membrane stretched upon stiff horny semi-rings, doubtless composed of chitine, and certainly not muscular. By bringing the outline of the rounded exterior into focus, we see that these rings form sharp ridges ; and by tracing them onwards to the attenuated extremity of the organ, we see them gradually give way to transverse lines of interrupted ridgy warts upon the outside of the membrane. ‘The true muscles appear to be indicated by those oblique lines and bands that are seen in the interior, beneath the horny rings. 1890 EVENINGS AT THE MICROSCOPE. This specimen shows very distinctly that the two sides are but semi-tubular, and as one pair of the op- posing edges are open at each extremity, and the other pair separate throughout, we are able to discern very clearly the array of hooks, by which the edges are united at the will of the animal. No trace of the curious little point- ed barrel-shaped papille is found here, but I have seen it in other examples. It seems highly probable, from the observations of the excellent wie gUCKER OF A euresriy, 2atomist just named, that the ex- A small portion of: one half-cylinder.” hanstion of the neciar Ola gious which is effected with great rapidity and completeness, is a process dependent on respiration, and connected with the air-pipe that permeates each division of the sucker. It will not be a very violent transition, if from the sucking pump of the Butterfly I carry you to the silk- spinner of the caterpillar. Here I have a Silkworm in the act of commencing its cocoon ; by inclosing which in this glass tube, we shall conveniently have the insect at command, and shall be able to view the process un- der a low magnifying power and reflected light. Now the grey face of the worm is presented to us; and we ean see, below the edge of the head-shield, a short broad upper lip, forming two blunt points. Below this is the pair of strong brown mandibles, convex outwardly and concave inwardly, each cut at its broad biting edge into several teeth. Below these are two little points which represent the mawille, and between them a blunt rounded knob, which is the lower lip (Cabiwm). INSECTS : THEIR MOUTHS. 181 You may also see, on each cheek, close to the base of the mandible, a little pit, out of which rises a short columnar organ tipped with two bristles ; these columns are the incipient antenne. Outside them you may dis- cern on each cheek, a series of six globes of glass (so they appear) set in the substance of the skin,—tive form- ing a semicircle, and one in the centre; these are “the windows at which the [silkworm’s] soul looks through,” —provided he has any soul—in prosaic parlance, his eyes. Now, having thus introduced the several members of our useful friend’s physiognomy to yon, let me call your attention to a fleshy wart just beneath the lower lip, and midway between the baser of the two fore legs. This wart terminates in a horny point not unlike a bird’s beak, which is perforated, and from the tip of which the glistening yellow filament of silk is ever drawn ont, as the caterpillar throws his head from side to side. This pointed wart is the spinning organ; and the thread of silk is, as it issues from the orifice, a fluid gum, which hardens immediately on its exposure to the air. The silk-gum is secreted by the caterpillar in two long blind tubes, which lie twisted and coiled in the interior of the body, occupying nearly the whole space, except that which is taken up by the great digestive canal. These become very slender as they approach the head, and at length terminate in a dilated reservoir, which opens by the little pointed wart which you have just seen. Many caterpillars are able to suspend themselves at pleasure by means of the thread which they are spin- ning, lengthening it and “stopping it off,” at will. This latter operation they perform (though they cannot recal the thread when once it has issued) by means of an an 182 EVENINGS AT THE MICROSCOPE. gular point formed by the two slender tubes at their junction in the reservoir; thus compressing thie thread of gum, and so preventing any more from issuing. The gum is perfectly colourless in the reservoir, but as it issues forth becomes coated with a varnish, which is secreted in the same organ, and which is poured out at the same time. In the case of the common Silkworm, this varnish imparts to the silk that brilliant yellow hue which it generally possesses, and which, as the varnish is soluble, can be easily discharged from it in the man- ufacture. INSECTS : THEIR EARS AND EYES. 183 CHAPTER, x. INSECTS ! THEIR EARS AND EYES. A very wide field of observation, and one easily cul- tivated, is presented by the organs of sense in the in- sect races, and in particular by those curious jointed threads which proceed from the front or sides of the head, and which are technically called antenne. These may sometimes be confounded with the palp7, examples of which organs we have been lately looking at; for in a carnivorous Beetle, for instance, both palpi and antenne are formed of a number of oblong, polished hard joints, set end to end, like beads on a necklace, And it is probable there may be as much community in the function as in the form of these two sets of appendages ; that both are the seats of some very deli- cate perceptive faculty allied to touch, but of which we cannot, from ignorance, speak very definitely. It is likely, indeed, that sensations of a very variable char- acter are perceived by them, according to their form, the degree of their development, and the habits of the ppecies. It is not impossible, judging from the very great diversity which we find in the form and structure of these and similar organs in this immense class of beings, compared with the uniformity that prevails in the or- gans of sense bestowed on oursclves and other verte L184 EVENINGS AT THE MICROSCOPE. brate animals,—that are far wider sphere of perception is open to them than tous. Perhaps conditions that are appreciable to us only by the aid of the most deli- cate instruments of modern science may be appreciable to their acute faculties, and may govern their instincts and actions. Among such we may mention, conjec- turally, the comparative moisture or dryness of the at- mosphere, delicate changes in its temperature, in its density, the presence of gaseous exhalations, the prox- imity of solid bodies indicated by subtile vibrations of the air, the height above the earth at which flight is per- formed, measured barometrically, the various electrical conditions of the atmosphere ; and perhaps many other physical diversities which cannot be classed under sight, sound, smell, taste, or touch, and which may be alto- gether unappreciable, and therefore altogether incon- ceivable, by us. It is probable, however, that the an- tenne are the organs in which the sense of hearing is specially seated ; a conclusion which has long been con- jecturally held, and which is confirmed by some obser- vations recently made on the analogous organs in the Crustacea, which I will allude to more particularly presently. The forms which are assumed by the antenne of Insects are very diverse; and I ¢an bring before you only a very small selection out of the mass. One of the most simple forms is that found in many Beetles, as in this Carabus for example. Here, each antenna is zomposed of eleven joints, almost exactly alike and asymmetrical, each joint a horny body of apparently a long-oval shape, polished on the surface, but not smooth, because covered with minute depressed lines, and clothed with shaggy hair. There is, however, a slight INSECTS : THEIR EARS AND EYES. 185 illusion in the appearance: it seems as if the dividing point of the joints were, as I have just said, at the ter- mination of the oval, but when we look closely we see that the summit of each oval is, as it were, eut off by a line, and by comparing the basal joints with the others, we see that this line is the real division, that the sum- mit of the oval really forms the bottom of the succeed- ing joint, and that the constricted part is no articula- tion at all. The first, or basal joint (called the scapus), and the second (called the pedicella), differ in form from the rest, here but slightly, but often considerably. The whole of the remaining joints are together termed the clavola. You may sce a considerable diversity of figure und of aspect generally in this tiny Weevil, which may be accepted as a representative of a great family of Beetles, the Curculionide. The manner of their in- sertion strikes us at first sight as peculiar, as is in fact the aspect of the whole head. Instead of a thick sub- stantial solid front, with powerful widely-gaping jaws, such as we saw in the Carabus, here projects from be- tween the eyes a long rod-like proboscis, as long as the whole animal besides, curving downwards, and carry- ing at its very extremity a minute mouth, with all the proper apparatus of lips, jaws, and palpi. Moreover, the antenne are planted on thie two sides of this beal:, about its mid-length ; and they are curiously elbowed, each projecting horizontally at a right angle to the beak for a considerable distance, and then with a sharp angle becoming parallel to it for the remainder of their length. So that, supposing the terminal half of the beak to be broken off just behind the insertion of the antenne, the whole would compose the letter T. Now, L86 EVENINGS AT THE MICROSCOPE. the first bend of this angle is composed of a single joint, the scapus, which is, in this family, greatly lengthened ; and then the two or three final joints are much thicker than all the others, and are as it were fused together into a large oval knob, called the club. Now, a word or two in explanation of this very sin- gular form of head and head-organs. The larva or grub stage of these insects is destined to be passed in the interior of fruits and seeds; the individual which we have been examining (Lalaninus nucum) was born one morning in August in the interior of a hazel-nut. Its parent had chosen a suitable nut, just then when it is set for fruit, and as yet green and soft; and had with her proboscis, or rather with her jaws at its tip, as with a gimlet, bored a tiny hole through the yielding shell into the very interior; then turning round, and inserting the extremity of her abdomen with its ovipos- itor, she had shot an egg into this dark cavity. The juices poured forth at the wound soon healed the ori- fice; the nut grew; and presently the egg became a little white grub. He then rioted in plenty ; prolonged his darkling feast “From night to morn, from morn to dewy eve ;” —’twas all “dewy eve” to him, by the way, for no ray of light saw he, till that prosperous condition of existence was done. No wonder he grew fat; and fat those rogues of nut-weevils always are, as you well know. Well, when the nut fell, in October, the kernel was all gone, completely devoured, and our little high- way-robber was ready for his winter sleep: he gnawed a fresh hole through the now hard shell, made his way INSECTS: THEIR EARS AND EYES. 187 out, and immediately burrowed into the earth, where he lay till June; then became a pupa, and emerged just what you see him, a long-snouted beetle like his mother, in the beginning of August. Such is his * short eventful history ;” and you now see that the long beak is formed entirely with reference to this economy ; it is an auger fitted to bore holes into shell-fruits through their envelopes, for the reception of egos. There is a very extensive family of Beetles known as Lamellicornes, because the antennal joints are sin- gularly flattened and applied one over the other like the leaves of a book (lamella, a leaf). ITlere is a very common little Chafer found on the droppings in pas- tures (Aphodius jimetarius), in which the last three ANTENNA OF COCKCITAFER. joints constituting the club of the antenna, are of an ovate form, and flattened, so as to lie one on another quite close, like three oval cakes ; and being connected only at one end of the long axis, they open and shut at 188 EVENINGS AT THE MICROSCOPE. the pleasure of the animal, like a long pocket memo- randum-book of three leaves. But this structure is seen to still greater advantage in the much larger Cockchafer, so abundant in May in some seasons. For here the joints’ composing the club are much more numerous (seven in the male, six in the female), and they are proportionally longer and thinner, and therefore more leaf-like. The insect widely expands them, evidently to receive impressions from the atmosphere; when alarmed, they are closed and withdrawn beneath the shield of the head, but on the first essay towards escape, or any kind of forward movement, the leaves are widely opened, and then after an instant’s pause to test the perceptions on the sensorium, away it travels. In some Beetles each joint of the series has one of its outer angles more developed than the other, and so produced as to make, with the rest of the joints, a saw- like edge: you may see an example in this Click-beetle or Skipjack (Z7ater); but many members of the same family show the same structure in a far higher degree, the angle being drawn out in a long slender rod, whicn (with its fellows) imparts to the antenna the appearance of a comb. But much more curious and beautiful are the an- tenn of many Moths, which often resemble feathers, particularly in the group Lombycina, of which the Silkworm is an example; and in the male sex, which displays this structure more than the female. But I will show you a native example. This is the antenna of a large and handsome, and not at all uncommon moth—the. Oak Egger (Lasio- campa quercis). It consists of about seventy joints, so INSECTS: THEIR EARS AND EYES. 189 nearly alike in size and outline, that the whole forms an almost straight rod, slightly tapering to the tip. Each joint, however, sends forth two long straight branches, so disposed that the pair make a very acute angle, and the whole double series of seventy on each side, form a deep narrow groove. These two series of branches, being perfectly regular and symmetrical, impart to the antennee the aspect of exquisite feathers. It is, however, when we examine the elements of this structure in detail, using moderately high powers of enlargement, that we are struck with the elaborate- ness of the workmanship bestowed upon them. Each of the lateral branches is a straight rod, thick at its origin, whence it tapers to a little beyond its middle, and then thickens again to its tip. Here two horny spines project from it obliquely, one much stouter than the other, at such an angle as nearly to touch the tip of the succeeding branch. Besides this, each branch is surrounded throughout its length with a series of short stiff bristles, very close- set, projecting horizontally (to the plane of the axis of the branch), and bent upwards at the end candelabrum- fashion. The mode in which they are arranged is in a short spiral, which makes about forty-five whorls or turns about the axis; at least in the branches which are situated about the middle of the antenna, for these diminish in length towards the extremity, bringing the feather to a rather abrupt point. The entire surface of the branch gleams under re- flected light with metallic hues, chiefly yellows and bronzy greens; which appear to depend on very mi- nute and closely-applied scales that overlap each other. The main stem of the feather,—that is, the primary rod 190 EVENINGS AT THE MICROSCOPE. or axls,—is somewhat sparsely clothed with scales of another kind, thin, oblong, flat plates, notched at the end, and very slightly attached by means of a minute stem at the base,—the common clothing-scales of the Lepidoptera,—specimens of which we have before ex- amined. We may acquire some glimpse of a notion why this remarkable development of antennee is betowed upon the male sex of this moth, by an acquaintance with its habits. It has been long a practice with entomologists, when they have reared a female moth from the chry- salis, to avail themselves of the instincts of the species to capture the male. This sex has an extraordinary power of discovering the female at immense distances, and though perfectly concealed; and will crowd to- PORTION OF ANTENNA OF OAK EGGER MOTIL wards her from all quarters, entering into houses, beat- ing at windows, and even descending chimneys, to come at the dear object of their solicitude. Collectors call this mode of procuring the male “ sembling,” that INSECTS : THEIR EARS AND EYES. 191 is, “ assembling,” because the insects of this sex assemble at one point. It cannot be. practised with all insects, nor even with all moths; those of this family, Bomby- cide, are in general available; and of these, none is more celebrated for the habit than the Oak Egger. The very individual whose antenna has furnished us with this observation was taken in this way ; for hav- ing bred a female of this species the evening before last, I put her into a basket, in my parlour. One male, the same evening, came dashing into the kitchen; but yes- terday, soon after noon, in the hot sunshine of August, no fewer than four more males came rapidly in succes- sion to the parlour window, which was a little open, and, after beating about the panes a few minutes, found their way in, and made straightway for the basket, totally regardless of their own liberty. It must be manifest to you that some extraordinary sense is bestowed upon these moths, or else some ordi- nary and well-known sense in extraordinary development. It may be smell; it may be hearing ; but neither odour nor sound, perceptible by our dull faculties, is* given forth by the females; the emanation is far too subtile to produce any vibrations on our sensorium, and yet sufficiently potent, and widely diffused, to call these males from their distant retreats in the hedges and woods. I think it highly probable that the great in- crease of surface given to the antennee by the plumose ramification we have been observing, is connected with the faculty ; perhaps every bristle of the spiral whorls is a perceptive organ, constructed to vibrate with the tender undulations that circle far and wide from the new-born female. Surely the ways of God in creation, as well as in moral government, are “ past finding out!” 192 EVENINGS AT THE MICROSCOPE. The male Gnat presents in its antennz a pair of plumes of equal beauty, but of a totally different char- acter. The pattern here is one of exceeding lightness and grace, as you may see in this specimen. Each an- tenne is essentially a very slender cylindrical stem of many joints (about fourteen) ; at each joint springs out a whorl of fine hairs of great length and delicacy, which radiate in various directions (not, however, forming a complete circle), curving upward like the outline of a saucer, supposing the stem to be inserted into its centre. The length of these hairs is so great that the diameter of their sweep equals, if it does not exceed, the whole length of the antenna. In the tribe of two-winged insects, which we term, par excellence, Flies (Muscade), the antenn are of peculiar structure. The common House-fly shall give us a good example. Here, in front of the head, is a shell-like concavity, divided into two by a central ridge. Just at the summit of this project are the two antenne, originating close together, and diverging as they pro- ceed. Each antenna consists of three joints, of which the first is very minute, the second is a reversed cone, and the third, which is large, thick, and ovate, is bent abruptly downwards immediately in front of the con- cavity. From the upper part of this third joint pro- jects obliquely a stiff bristle or style, which tapers to a fine point. It is densely hairy throughout; and is more beset with longer hairs, on two opposite sides, which decrease regularly in length from the base, mak- ing a wide and pointed plume. Such are a few examples of what are presumed to be the ears of Insects; let us now turn our attention to their eyes. And we can scarcely select a more bril- INSECTS : THEIR EARS AND EYES. 193 liant, or a larger example, than is presented by this fine Dragon-fly (Zina), which I just now caught as it was hawking to and fro in my garden. Low gorgeously beautiful are these two great hemispheres that almost compose the head, each shining with a soft satiny lustre of azure hue, surrounded by olive-green, and marked with undefined black spots, which change their place as you move the insect round ! Each of these hemispheres is a compound eye. I put the insect in the stage-forceps, and bring a low power to bear upon it with reflected light. You see an infinite number of hexagons, of the most accurate symmetry and regularity of arrangement. Into those which are in the centre of the field of view, the eye can penetrate far down, and you perceive that they are tubes; of those which recede from the centre, you dis- cern more and more of the sides; while, by delicate adjustment of the focus, you can see that each tube is not open, but is covered with a convex arch, of some glassy medium polished and transparent as crystal. There are, according to the computations of accurate naturalists, not fewer than 24,000 of these convex lenses in the two eyes of such a large species of Dragon fly as this. Every one of these 24,000 bodies represents a per- fect eye; every one is furnished with all the apparatus and combinations requisite for distinct vision; and there is no doubt that the Dragon-fly looks through them all. In order to explain this, I must enter into a little technical explanation of the anatomy of the organs, a3 they have been demonstrated by careful dis- section. The vtassy convex plate or facet in front of each 9 194 EVENINGS AT THE MICROSCOPE. hexagon is a cornea, or corneule, as it has been called. Behind each cornea, instead of a crystalline lens, there descends a slender transparent pyramid, whose base is the cornea, and whose apex points towards the interior, where it is received and embraced by a translucent cup, answering to the vitreous humour. This, in its turn, is surrounded by another cup, formed by the ex- pansion of a nervous filament arising from the ganglion on the extremity ot the optic nerve, a short distance from the brain. Each lens-like pyramid, with its vit- reous cup and nervous filament, is completely sur- rounded and isolated by a coat (the choroid) of dark pigment, except that there is a minute orifice or pupil behind the cornea, where the rays of light enter the pyramid, and one at the apex of the latter, where they reach the fibres of the optic nerve. Each cornea isa lens with a perfect magnifying power, as has been proved by separating the entire compound eye by maceration, and then drying it, flat- tened out by pressure, on a slip of glass. When this preparation was placed under the microscope, on any small object, as the points of a forceps, being interposed between the mirror and the stage, its image was dis- tinctly seen, on a proper adjustment of the focus of the microscope, in every one of the lenses whose line of axis admitted of it. The focus of each cornea has been ascertained by similar experiments to be exactly equal to the length of the pyramid behind it, so that the image produced by the rays of light proceeding from any external object, and refracted by the convex cornea, will fall accurately upon the sensitive termina- tion of the optic nerve-filament there placed to receive it. INSECTS : THEIR EARS AND EYES. 195 The rays which pass through the several pyramids are prevented from mingling with each other by the isolating sheath of dark pigment; and no rays, except those which pass along the axis of each pyramid, can reach the optic nerve; all the rest being absorbed in the pigment of the sides. Hence it is evident, that as no two cornex on the rounded surface of the compound eye can have the same axis, no two can transmit a ray of light from the very same point of any object looked at; while, as each of the composite eyes is immovable, except as the whole head moves, the combined action of the whole 24,000 lenses can present to the sensorium but the idea of a single, undistorted, unconfused object, probably on somewhat of the same principle by which the convergence of the rays of light entering our two eyes gives us but a single stereoscopic picture. The soft blue colour of this Dragon-fly’s eyes—as -also the rich golden reflections seen on the eyes of other insects, as the Whameflies, and many other Dip- tera—is not produced by the pigment which I have alluded to, but isa prismatic reflection from the cor- nee. You would suppose that, having 24,000 eyes, the Dragon-fly was pretty well furnished with organs of vision, and surely would need no more ; but you would be mistaken. It has three other eyes of quite another character. If you look at the commissure or line of junction of the two compound eyes on the summit of the head, you will see, just in front of the point where they sep- arate and their front outlines diverge, a minute cres- cent-shaped cushion of a pale-green colour, at each angle of which is a minute antenna. Close to the base 196 EVENINGS AT THE MICROSCOPE. of each antenna there is set in the black skin of the head that divides the green crescent from the com- pound eyes, a globose, polished knob of crystal-like substance, much like the “ bull’s-eyes” or hemispheres of solid glass that are set in a ship’s deck to enlighten the side-cabins. On the front side of the crescentic cushion there is a third similar glassy sphere, but much larger than the two lateral ones. What are these three spherules ? They are eyes, in no important respect differing from the individuals which compose the compound masses, except that they are isolated. The shining glassy hemisphere is a cornea of hard transparent sub- stance, behind which is situated a spherical lens, lodged in a kind of cup formed by an expansion of the optie nerve, and which is surrounded by a coloured pigment- layer. You may study these simple eyes, or stemmata as they are called, in many other insects, though they are not so universally present as the compound eyes. On the forehead of the Honey-bee they are well seen, as three black shining globules, placed, as in the Dragon fly, in a triangle. CRABS AND SHRIMPS. 197 CHAPTER XI. CRABS AND SHRIMPS. Ir is always interesting to trace the varied forms and conditions under which any particular function is verformed ; and particularly to mark, in creatures very remote from us in the scale of being, the organs devoted to the senses which are so requisite to our own comfort. We have already seen some of these diversities, in ex- amples taken from the classes Mollusca and Insects ; _and will. now examine some more, as they appear in the Crustacea. If you look at the head of a Crab, a Lobster, or a Prawn, you will see that it is furnished with jointed antenne, like that of Insects; but whereas in insects there is never more than a single pair, in the creatures of which I am speaking there are two pairs. In the Prawn you may suppose, at first sight, that there are four pairs; but that is because the internal antenne terminate each in three many-jointed bristles, in strue- ture and appearance exactly like the bristles of the outer pair, two of the three being nearly as long as the outer, while the third is short. In the Lobster, the in- ternal are two-bristled, both bristles rather short, while the external are very long. In the Flat-crabs each pair is simple, the inner minute, the outer long. In the L98 EVENINGS AT THE MICROSCOPE. great Eatable Crab each pair is very small, and they are dissimilar. Now taking the last-named animal as the repre sentative of his class, let us examine one of his inner antenne first. It consists of a jointed stem and a terminating bristle; the latter furnished with small hairs common to the general surface of the body, and with long, delicate, membranous filaments (set), often improperly called ez/ia, which are larger, and much more delicate in structure than the ordinary hairs. The basal joint is greatly enlarged: if it be eare- fully removed from its connexion with the head, and broken open, it will be found to enclose in its cavity a still smaller chamber, with calcareous walls of a much more delicate character that the outer walls. This in- ternal shell is considered by Mr. Spence Bate to be a cochlea, from its analogy, both in structure and sup- posed use, to the organ so named in the internal ear of man and other vertebrate animals. It is situated, as has been said, in the cavity of the basal joint of the internal antenna, and is attached to the interior surface of its wall farthest from the median line of the Crab. It has a tendency to a spiral form, but does not pass beyond the limits of a single convolu- tion, If this interior cell does indeed represent the cochlea of more highly-constructed ears,—to which it bears some resemblance, both in form and structure,—then it seems to identify, beyond dispute, these inner or upper antennee as the organs of hearing. Now with this conclusion agrees well the manner in which the living animal makes use of the organs in CRABS AND SHRIMPS. 199 question. The Crab always carries them erect and elevated; and is incessantly striking the water with them, with a very peculiar jerking action, now and then vibrating, and, as it has been called, ‘“‘twiddling” them. These antenne, therefore, ap- pear to be always on the watch :—let the animal be at rest, let it be feeding, no mat- ter, the superior atennze are ever elevated and on con- stant guard. The lengthened and delicate setee with which they are furnished, are, moreover, peculiarly adapted to re- ceive and convey the most minute vibratory sensations from the medium in which they are suspended ; and, on the whole, it seems to be satisfactorily settled by Mr. Spence Bate (to whose excellent memoir® I am in- debted for these explanatory details) that the inner an- tenn are real ears. Having thus taken our Crab by the ears, we will endeavour next to tweak his nose. But stay, we must find it first. We turn our horny gentleman up, and in his flat ancient face we certainly discern little sign of a nasal organ. Our friend Mr. Bate must assist us again. He will tell us to look at the outer or lower antenne. We will look accordingly, magnifier in hand, while he makes it clear to us that these are a pair of noses. Each of these organs is formed of a stem consisting in general of five joints, and a filament of many min- ute joints. In the Prawn and the Lobster all the five * Annals of Nat. Hist. for July, 1855. EAR OF CRAB, FROM BEHIND. 200 EVENINGS AT THE MICROSCOPE. joints of the stem are distinct; but in the Crab the whole are, as it were, soldered together into a compact mass, with difficulty distinguishable into their constit- uent articulations ; while in some species their position ean be indicated only by the presence of the olfactory operculum. This important little organ varies in its construc- tion in the different families of Crustacea. In the Crab it is a small movable appendage, situated at the point of junction between the second and third joints; itis attached to a long calcareous lever-like tendon, at the extreme limit of which is placed a set of muscles, by which it is opened and closed ; to assist in which operation, at the angle of the operculum most distant from the central line of the animal are fixed two small hinges. When the operculum is raised, the internal surface is found to be perforated by a circular opening protected by a thin mem- brane. In the Prawn, Shrimp, and Lobster, there is no operculum, but only the orifice covered by a mem- brane, which is placed at the extremity of a small pro- tuberance, and it is not capable of being withdrawn into the cavity of the antenna, as in the Crab. In the latter animal, the little door, when it is raised, exposes the orifice in a direction pointing to the mouth ; and where there is no door, still the direction of the opening is the same, inwards and forwards, an- swering to the position of the nostrils in the higher animals. In each case it is so situated that it is im- possible for any food to be conveyed into the mouth without passing under this organ ; and there most con- veniently the animal is enabled to judge of the suit- CRABS AND SHRIMPS. 201 ability of any substance for food, by raising the little door, and applying to the matter to be tested the sensi- tive membrane of the internal orifice. Thus it is concluded that this lower or outer pair of antenne are the proper organs of smell, as the upper and inner are of hearing.* The eyes, though constructed on the same gencral principles as those of Insects, yet present some partic- ulars worthy of your notice. In the Crabs and Lob- sters they consist of numerous facets, behind each of which is a conical or prismatic lens, the round extrem- ity of which is fitted into a transparent conical pit, corresponding to a vitreous body, while the conical ex- tremity of these lenses is received into a kind of cup, formed by the filaments of the optic nerve. Each of these filaments, together with its cup, is surrounded by pigment matter in a sheath-like manner. To see this structure would require anatomical skill ; but you may here examine with a low power portions of the cor- nea, or glassy exterior, of the eye of a Crab and of a Lobster. In the former, you see that the facets into which the cornea is divided are hexagonal, like those of most Insects, but in the latter they are square. But Crustacea have a far greater faculty of cireum- spection than insects have; for besides the extensive convexity and numerous facets of their eyes, these or- gans are placed at the extremity of shelly foot-stalks, which are themselves movable on hinges, capable of being projected at pleasure, and of being moved in different directions, and of being packed snugly away, when not in active use, in certain grooves hollowed * Op. cit. Q* 302 EVENINGS AT THE MICROSCOPE. out expressly for them in the front margin of the shell. If ever you should chance to meet with the exotic Crustacea of the genera Coryceus and Sapphirina, you would see a form of eye of a quite remarkable and unique character. It is described by Dana in the fol- lowing terms :— “A pair of simple eyes consisting of an internal prolate lens, situated at the extremity of a vermiform mass of pigment, and of a large, oblate lens-shaped cornea. The cornea is connected intimately with the exterior shell of the front or the under side of the head, and the two cornes are like spectacles adapted to the near-sighted lenses within ; their size is extraordinary, being often one-third of the greatest breadth of the body in Coryceus. The lens and the cornea are often very distant from each other, being separated by a long clear space. The external surface of the cornea is spherical ; but the inner is conoideo-spherical, or para- bolic. The texture is firm, and when dissected it breaks or cuts like a crystalline lens. The true lens is always prolate, with a regular contour, excepting be- hind, where it is partly penetrated by the pigment. The pigment is slender, vermiform, of a deep colour, either red or blue, but at its anterior extremity usually lighter, and often orange or yellow.” * We might find much more both instructive and amusing in examining microscopically the structure of the higher Crustacea; but we will now dismiss them in order to discuss some of the lower forms, many of which are so minute that their whole bodies may be watched with ease performing all the functions of life, * Rep. on Crust. p. 1026. CRABS AND SHRIMPS. 2038 while confined under our eye, on the stage of the mi- croscope. I refer to the tiny active little creatures known as Water-fleas, which are abundant in both fresh and salt water. In this jar of fresh water which has been standing in the window for weeks, you may see among the green filaments of Chara many little atoms which scuttle hither and thither with a rapid succession of snort leaps. These belong to the genus Cyclops, and are Crustacea, belonging to the order Enromosrraca. By the aid of a glass tube which I stop at one end with my finger, I will endeavour to catch one. It is no easy matter, as you see, for the instant the end of the tube is brought near to one, he takes the alarm and leaps nimbly away before I can make the water rush in by withdrawing my finger from the other end. But I have one at length. Here it is:—a minim of life not more than a six- teenth of an inch in length, looking something like a pellucid egg, furnished with long antenne, with five pairs of branching feet, and a long tail terminating in bristles. But its parts and organs must not be dis- missed in this summary way; we must look at them in detail. And first of all, in the very midst of his forehead, like that obscene giant* after whom our tiny atom is named—he bears a single eye that glares like a ruby. It would need no vast beam of olive-wood sharpened and heated in the fire, and “twirled about” by the united strength of five heroes, to “grind the pupil out ;” for though brilliant and mobile, it is far too mi- nute to be touched by the tip of the finest needle. Yet. * Odyss. IX. 204 EVENINGS AT THE MICROSCOPE. it is elaborately constructed ; for it consists of a nun ber (not very large) of simple eyes placed beneath a common glassy cornea. Several muscle-bands are at- tached to this compound organ of vision, and are ar- ranged so as to form a cone, of which the eye is the base; these give the eye a movement of rotation upon its centre, which may be distinctly seen. All the limbs, including both pairs of antennz, tw3 pairs of foot-jaws, five pairs of feet, and a pair of tail- lobes, are furnished at each of their many joints with tufts of long hairs; these appear to act the part of paddles, as the active little animal strikes the water vigorously with all its limbs, for the purpose of pro- gression, and also for the creation of currents in the fluid, which currents subserve a double object,—the bringing constant supplies of water to be respired, and floating atoms of food to be devoured. In this individual, which is a female, the antennze are nearly equal in size throughout their length; but in the male, the middle joints of the upper pair are re- markably enlarged, forming a large swelling, followed by a sudden contraction, the first part of which is hinged. Allof the true feet, and the second pair of foot-jaws, are divided to the base into two equal branches, so that the animal seems to possess no fewer than twenty-six limbs each of which being many-jointed, and each joint, as 4 have observed, being set with delicately plumose hairs, the whole effect is most elegantly light and feathery. On each side of the slender tail (more correctly, the abdomen) you see an oval bag connected with the body by an excessively slender thread of communication, and filled tensely with pellucid globose bodies. Like Jolin Gilpin, of equestrian fame, when CRABS AND SHRIMPS. 2U5 “He hung a bottle on each side To keep his balance true,” our little natatory harlequin “ carries weight.” But these bags are filled with eggs, a temporary provision for their due and proper exposure to the water, while yet they are protected from enemies. They are devel- oped only at certain seasons, when the eggs having at- tained a given amount of maturity in the ovary, are transferred through the exceedingly slender tube into these sacs, and are there carried about by the mother until the young are hatched, when the curious recep- tacles, being no longer needed, are thrown off, and specdily decay. Here is a second form. It is named Zynceus, and is nearly as common as the Cyclops in our stagnant pools. Essentially its structure is the same, but it has this peculiarity, that its body is enclosed within a trans- parent shell, which is thin and flattened sidewise, and through whose walls all the movements and functions of its parts are distinctly visible. The shell is broadiy ovate in outline, comes to a sharp edge above, but is open all along the lower half of its cireumference—as if two watch-glasses had been soldered together, edge to edge, and then a portion of the semicircumference had been ground away, so as to leave a thin but long entrance. Through this narrow orifice the limbs are protruded for locomotion, and through it the surrounding water finds its way in currents, bringing oxygen to be respired and food to be devoured. The translucent shell descends in front into a sharp Jong beak, below which are seen the organs of the mouth, two pairs of foot-jaws, beset with fine bristles. At the origin of the beak is the eye, consisting, as we 206 EVENINGS AT THE MICROSCOPE. saw in the Cyclops, of several lenses, enveloped in a common cornea, the whole forming a movable organ of a blue-black hue. Just behind this, at the very highest part of the shell, is a little colourless bladder- like vesicle, which constantly maintains a rapidly alter- nate contraction and dilatation. This is the heart, and this motion circulates the blood. Below this, there is seen a great translucent irregu- lar mass of flesh, evidently comprising many viscera, which winds along from one end of the shell to the other, nearly occupying its entire area, but not in con- nexion with it at the hinder part, as we see by its free movements there, where it curves round, and bending beneath terminates in a blunt tail, armed with two strong hooks, which can at pleasure be thrust down through the narrow orifice of the shell, and become par- tially straightened by being forcibly thrown backward This great central mass is mainly occupied by the ali- mentary canal, in which food in various stages of assim- ilation may at all times be seen, and in which the interesting function of digestion can be witnessed throughout, from the first seizure of the atom and its mastication by the jaws, to the discharge of the effete remains. The individual before us does not carry at this time egos in the process of development; but the deficiency is supplied by a Daphnia which is playing about in the same drop of water. Here you perceive, between the arched outline of the shell and the sinuous outline of the free soft body, an open space of some size, which con- stitutes a receptacle, in which the eggs are deposited as they are laid, and in which they remain not only until the little animals are hatched, but until they have ae: CRABS AND SHRIMPS. 207 quired a sufficient maturity to swim about and get their independent living. This receptacle—in which you may see five or six eges—is freely open to the surrounding water, which enters the slit edge of the shell, behind the tail. Per- haps you wonder why the eggs are not washed out by the respiratory currents; they are in fact maintained in DAPHNIA. their position only by a slender tongue-like projection from the back of the parent, which appears to have that special object. When, however, the young are ready for freedom, the mother has but to depress her body a little more than ordinary, when the door is opened, and the young easily slip from the receptacle into the open water. These tiny odd-looking sprawling things that you see moving about by quick jerks in the same drop of water, are the young recently hatched. They are quite unlike their parent, having as yet no bivalve shell, no abdomen, and only three pairs of limbs. The body is a 208 EVENINGS AT THE MICROSCOPE. transparent plate, resembling the bowl of a spoon in form, but ending in two points which carry pencils of bristles. The large dark eye is conspicuous in front, and the six jointed and bristled limbs radiate from the centre, projecting stiffly on all sides. The second and third pair are seen to be double, each giving off a branch, which is pencilled with bristles like the principal stem. We have not yet done with these tiny Water-fleas. The sediment at the bottom of this jar of water is quite alive with a host of nimble atoms, some of which you may see crawling up the sides of the glass. They are quite distinct from either of the kinds we have been examining, not only in details of structure, which is more identical indeed than it seems at first sight, but in habit; for whereas they shoot to and fro through the water with great force and rapidity, these can scarcely swim at all; or, if they do, it is with comparative slow- ness and much apparent effort ; though over the smooth side of their glass dwelling, or upon the stems of water- plants, they glide along with much ease and elegance, by the quick vibrations of their pencilled feet. The form we are now contemplating is distinguished by the name of Cypris, a genus which contains a good many British species. It is more completely inclosed in a shell than even the Lynceus, and its envelope more truly resembles the shell of a bivalve Mollusk, for the valves are open for more than three-fourths of their cir- cumference ; while the portion of the back that is united is sufficiently elastic to allow of some degree of expan- sion, thus answering the purpose of a hinge. Now look at the elegant little creature. Its most prominent feature is its two pairs of antennee, one pro- jecting forwards and curved upwards, the other down- CRABS AND SHRIMPS. 209 wards. Both consist of several transparent joints, and are tipped with long clear bristles; but the pencils which tip the upper pair are specially graceful, being as long as the whole shell, exceedingly slender, beauti- fully curved, and so transparent that they seem formed of spun glass. Another peculiarity is that there seems to be but one pair of legs, which terminate each in a hooked spine. You now and then sce these awkwardly thrust out from beneath the hinder part of the shell, but loco- motion is principally effected by the pencilled antenne. cCYPris. There is, however, a second pair of legs, but these do not usually make their appearance outside the shell, being curved backwards to sustain the ovaries. About thirty years ago an Irish naturalist, Dr. J. Vaughan Thompson, announced a discovery, which, oversetting conclusions previously received by all, caused no little dissent and opposition, and gave rise to a lengthened and wide spread controversy. A very minute crustaceous animal was known, as inhabiting the open sea, to which the name of Zoea had been given. 210 EVENINGS AT THE MICROSCOPE. It had sessile eyes, and was remarkable for having a long spine projecting from the face, and a similar one standing up from the centre of the back. Another form was known, which constituted the genus M/egalopa: in which the body was broad, the eyes stalked, and the abdomen projecting behind. This was also smail, but somewhat larger tlian the preceding. Nobody suspected that these were other than inde- pendent forms of animal life, distinct from each other, and equally distinct from every known genus of Crus- tacea besides. It was supposed that no animal of this class underwent metamorphosis,—or that change of form in different periods of life which distinguishes Insects : but that these creatures retained through life the general shape, slightly modified by development of parts and organs, which they each displayed when hatched from the egg. But these conclusions were quite set aside by the brilliant discovery of Thompson, that Zoea and Mega- lopa were the same animal in different stages of exist- ence ; and that, moreover, both were but the early states of well-known and familiar forms of larger Crustacea, which therefore undergo a metamorphosis as complete as that by which the caterpillar changes to a chrysalis, and the chrysalis to a butterfly, and in every essential point parallel to it. In the Cove of Cork this naturalist met with a con- siderable number of Zoeas, which he kept in captivity. Some of these passed into the Dfegalopa form, which in turn changed to the most abundant of our larger Crus- tacea, the common Shore-crab (Carcinus menas). “Thus, in its progress from the egg to its final development, the Crab was proved to pass through two temporary condi CRABS AND SHRIMPS. 211 tions, which had previously been regarded as types, not of genera only, but of different families ; and both strik- ingly dissimilar from the group to which, in its perfect state, it belongs.” Ihave not myself examined the transformations of this species; but, as they have been well worked ont, and as the animal is so abundant everywhere on the coast that you may easily verify what has been ob- served, I will cite you the elaborate account of Mr. R. Q. Couch of Penzance, who has investigated the subject with great skill, zeal, and success. Having procured some specimens of the Shore-crab laden with eggs, just ready for shedding, lie goes on to say,— these were transferred to captivity, placed in separate basins, and supplied with sea-water; and in about sixteen hours I had the gratification of finding large numbers of the creatures alluded to above swim- ming about with all the activity of young life. There could be but little doubt that these creatures were the young of the captive Crabs. In order, however, to se- eure accuracy of result, one of the Crabs was removed to another vessel, and supplied with filtered water, that all insects might be removed ; but in about an hour the same creatures were observed swimming about as be- fore. To render the matter, if possible, still more cer- tain, some of the ova were opened, and the embryos ex- tracted ; but shortly afterwards I had the pleasure of witnessing, beneath the microscope, the natural burst- ing and escape of one precisely similar in form to those found so abundantly in the water. Thus, then, there is no doubt that these grotesque-looking creatures are the young of the Carcinus menas ; but how different they are from the adult need hardly be pointed out any fur- 912 EVENINGS AT THE MICROSCOPE. ther than by referring to the figure. When they first escape they rarely exceed half aline in length. The body is ovoid, the dorsal shield large and inflated; on its upper edge and about the middle is a long spine, curved posteriorly, and rather longer than the diameter of the body, though it varies in length in different spe- cimens; it is hollow, and the blood may be seen cireu- lating through it. The upper portion of the body is ZOEA OF SIIORE-CRAB. sap-green, and the lower semi-transparent. The eyes are large, sessile, and situated in front, and the cirenm- ference of the pupil is marked with radiating lines. The lower margin of the shield is waved, and at its posterior and lateral margin is a pair of natatory feet. The tail is extended, longer than the diameter of the shield; and is composed of five equal annulations, besides the ter- minal one; its extremity is forked, and the external CRABS AND SHRIMPS. 213 angles are long, slender, pointed, and attached to the last annulation by joints. Between the external angles, and on each side of the median line, are three lesser spines, also attached to the last ring by joints. Between the eyes, and from near the edge of the shield, hangs ¢ long, stout, and somewhat compressed appendage, which, as the animal moves, is reflexed posteriorly be- tween the claws. Under each eye is another append- age, shorter, and slightly more compressed. The claws are in three pairs; each is composed of three joints, and terminates in four long, slender, hair-like appendages. These claws are generally bent on the body, but stand in relief from it. If the animal be viewed in front, the lower margin of the dorsal shield will be found to be waved into three semicircular festoons, the two external of which are occupied by the eyes, and between which the middle one intervenes; the general direction of the claws will be seen to be at right angles to the body. As the young lies inclosed within the membranes of the egg, the claws are folded on each other, and the tail is flexed on them so far as the margin of the shield, and, if long enough, is reflected over the front of the shield between the eyes. The dorsal spine is bent backwards, and lies in contact with the dorsal shield ; for the young, when it escapes from the egg, is quite soft, but it rapidly hardens and solidifies by the deposition of calcareous matter in what may be ealled its skin. The progress of this solidification may be very beautifully observed by watching the circulation in the doral spine. When the creature has just effected its liberation from the egg, the blood-globules may be seen ascending to the apex ; but as the consolidation advances, the circulation be- comes more and more limited in its extent, and is finally 914 EVENINGS AT THE MICROSCOPE. confined to the base. These minute creatures, in this early state of their existence, are natatory and wonder- fully active. They are continually swimming from one part of the vessel to the other, and when observed free in their native pools, are, if possible, even more active SECOND STAGE OF SIORE-CRAB. than when in confinement. Their swimming is pro- duced by continued flexions and extensions of the tail, and by repeated beating motions of their claws; this, together with their grotesque-looking forms, gives them a most extraordinary appearance when under examina- tion. As the shell becomes more solid they get less ac- tive, and retire to the sand at the bottom of the vessel, to cast their shells, and acquire a new form. They are CRABS AND SHRIMPS. 215 exceedingly delicate, and require great care and atten- tion to convey them through the first stage ; for unless the water be supplied very frequently and in great abundance, they soon die. “The second form of transmutation is equally as re- markable as the first, and quite as distinct from the adult animal. In the species now under consideration this second transformation is marked by the disappear ance of the dorsal spine ; the shield becomes flatter and more depressed, the anterior portion more horizontal and pointed, the three festoons having disappeared. The eyes, from being sessile, are now elevated on foot- stalks, the infra-orbital appendages become apparently converted into antennz. The claws undergo an entire revolution ; the first pair become stouter than the others, and are armed with a pair of nippers,”’ the others being simple; ‘‘ but the posterior pair are branched near the base, and one of the branches ends in a bushy tuft. The tail is greatly diminished in its relative size and propor- tions, and is sometimes partially bent under the body, but is more commonly extended. This form is as nata- tory as the first. They are frequently found congregat- ing around floating sea-weed, the buoys and strings of the crab-pot marks, and other floating substances, both near the shore and in deep water. Their general form somewhat resembles a Galathea.” * Thus under Mr. Couch’s eye the Zoea had changed toa MMegalopa ; and this latter became after a short time a Crab, in which were all the characters that be- long to the order to which the parent belongs; but not those of the genus, nor even of the family. Its form bore a close resemblance to that of the Sargasso * Rep. Cornw. Polyt. Soc. 1843. 216 EVENINGS AT TIIE MICROSCOPE. Crabs (Grapsidw); for the shield, instead of being large and arched in front, and narrowed behind, was nearly square, while the front was (taking in the eyes) almost straight, the lateral angles much advanced. This Crab, however, was still very minute; and many sloughings were before it. In the course of these it was destined gradually to attain not only the dimen- sions of its parents, but aiso their form. This, how- ever, would be matter of development, rather than y ii hy will tl = | iy | i THIRD STAGE OF SIORE-CRAB. n-etamorphosis: the lateral outlines of the shield would more and more approach each other behind, while the series of points that now belonged to these lateral out- lines would become thrown into the front margin, which would by degrees assume an arched form, as you may see in this figure of the adult Crab. Though I cannot at this moment show you speci- mens of the Carcinus in its earlier stages, yet I have here a good number of the Zoeas of one of those inter- mediate forms which are the connecting links between the Crabs and Lobsters:—I mean Galathea. The adult animal is of a broad squat form, something like what you might suppose a Lobster to be, if it had been flattened between two stones, without being actually CRABS AND SHRIMPS. 217 destroyed. We have two or three species, one of which is adorned with brilliant scarlet and azure paintings ; but I cannot tell to which of them all this infant form belongs. You perceive that there is a general similarity be- tween these transparent little creatures, and the Zoea described by Mr. Couch; but there are great differ- ences in detail. The glassy shield or carapace shoots out in front in a stiff, inflexible, very fragile spine. ADULT SHORE-CRAB,. This is perfectly straight, and nearly thrice the length of the whole shield. It is beset, on various lines on its surface, with short slender spinules jointed to shoulder- like angles, and not serratures. Its interior is perfo- rated by a canal, which dilates and narrows irregularly. The carapace posteriorly is semi-oval, projecting a trans- parent convex vault far over the part where the ab- 10 218 EVENINGS AT THE MICROSCOPE. domen is attached to it, as is seen when the latter bends down. Its extremity gradually tapers into two straight, sub-parallel, stiff spines, about as long as the carapace itself, each terminating in a hooked point. The abdomen ends in a spinous plate, which is very elegantly lozenge-shaped, and beset with spines. Each of the two latero-posterior edges of the lozenge is ent into six rectangular teeth, and each tooth bears on its hinder face a long spine articulated to it, and most del- icately plumose all along its sides. The hindermost pair of spines are short, and are set close together, side by side. Besides these jointed spines, each lateral angle of the caudal lozenge-shaped tail-plate projects into a spine-like tooth. Though the individuals before us are all in the same state as to the stage of their development, there is some difference in size, indicating, doubtless, a corre- sponding diversity in age. We will isolate a few of the largest, and put them into a glass trough for micro- scopical examination. The largest, during the few minutes which I have occupied in the process of dipping them out, has under- gone a metamorphosis. You observed that, after skip- ping about the trough for a few moments, it sank quietly to the bottom, where it lay on its back; the next thing that you see is a much more crab-like animal, more opaque, redder, much larger, but lying on its back in the very spot where a moment before you had seen a Zoca; while close by it lies the transparent filmy skin which has been cast off. The new animal is evidently now in its final state, needing only development of its parts, which it would obtain, if in freedom, hy successive moults, to acquire the adult form. CRABS AND SHRIMPS. 219 If we now submit the exuviz in detail to a power of 220 diameters, we shall obtain some interesting views of the structure. The slough of the eyes in par- ticular presents one of the most exquisite objects that you can behold. They are somewhat pear-shaped, with the facetted portion well defined. It is the ap- pearance of these facets, varying according as the per- fectly hexagonal outline of each or the smooth and glossy convexity comes into focus, that is so peculiarly charming. Returning now to the examination of one of the liv- ing Zoeas, you perceive that the three pairs of pencilled limbs do not represent any of the true legs; for the transparency of the integuments allowing the interior to be clearly seen, and the organs of the imago being matured and just ready for sloughing, you discern, with the most beautiful distinctness, the fingered claws (short and stumpy, it is true, as compared with their perfect form in the newly freed imago) folded down upon the breast within the skin, the second pair as large as these, and traces of others beneath them,—all these forming two great projecting lobes. Slightly movable, beneath the thorax of the Zoea, and oc- cupying a bulk nearly equal to that of the whole shield. The circulation of the blood is beautifully clear. The pellucid colourless globules chase each other by starts to and fro, as the eye rests on the outgoing or returning current. It is distinct in some parts where you would scarcely have looked for it; as all over the lozenge plate of the tail, in the interior of the eyes, throughout the posterior spines of the shield, and the frontal spine. But besides, and apparently indepen- 220 EVENINGS AT THE MICROSCOPE. dent of the circulation, there is a singular fusiform vessel in the latter segments of the abdomen penetrat- ing the tail-plate, on the ventral side. This vessel, now and then, at irregular intervals, dilates quickly and closes; the wave proceeding upward toward the head, but only for a short distance, and unattended with any impulse to the blood-globules. The nature of this vessel, and its use in the economy of the infant Crab, I can in no wise explain. BARNACLES. 221 CHAPTER XII. BARNACLES. You cannot have wandered among the rocks on our southern or western coasts, when the tide is out, with- out having observed that their whole surface, up to a certain level (often very precisely defined), is rough- ened with an innumerable multitude of little brownish cones. If you have ever thought it worth while to examine them with more care, you have seen that, crowded as they are, so thickly that frequently they erush each other out of their proper form and_pro- portions, they are all constructed on the same model. Each cone is seen to be a little castle, built up of stony plates that lean towards each other, but which leave an orifice at the top. Within this opening, provided the castle be tenuated by a living inhabitant, you sce two or three other pieces joined together in a pecu- liar manner, which are capable of separating, but which, when brought together, effectually close up all ingress. Perhaps you have never pushed your investigations farther than this, having a courteous respect for the feelings of the inmate, which has prevented your in- truding on a privacy so recluse. But I have been less considerate; many a time have I applied the steel 222 EVENINGS AT THE MICROSCOPE. chisel and hammer to the solid rock, and having cut off some projecting piece or angle, have transferred it, all covered with its stony cones, to the interior of a glass tank of sea-water, for more intimate acquaintance with the little builders at leisure. These are Barnacles (Galanide). Such a colony Ihave now in my possession, which I will submit to you, for they present a beautiful and highly interest- ing spectacle, when engaged in their ordinary employ- ment of fishing for a subsistence. And not only so, but I have living specimens of a much larger and finer species than the common one,—the Balanus porcatus, whose castle stands an inch or more in height. The structure, however, and habits are pretty much the same in both. Without disturbing the busy fishers, then, just take your seat in front of this tank, and with a lens before your eye, watch the colony which is seated on that piece of stone, close to the glass side. From one and another, every instant, a delicate hand is thrust forth, and presently withdrawn. Fix your attention on some one conveniently placed for observation. It is now closed; but in a moment, a slit opens in the valves within the general orifice, displaying a black lining with pale blue edges ; it widens to an oval; the pointed valves are projected, and an apparatus of delicate curled filaments is thrust quickly out, expanding and uncurling as it comes, to the form of a fan; then in an instant more the tips of all the threads again curl up, the threads collapse, and the whole apparatus is quickly withdrawn, and disappears beneath the closing valves. The next moment, however, they re-open, and the little hand of delicate fingers makes another grasp, an] BARNACLES. 223 so the process is continually repeated while this season of activity endures. Now, by putting this specimen into a glass trough, and placing it under a low power of the microscope, we shall see what an exquisite piece of mechanism it is. The little hand consists of twenty-four long fingers, of the most delicate tenuity, each composed of a great number of joints, and much resembling in this respect the antenne of a Beetle. These fingers surround the mouth, which is placed at the bottom of the sort of im- perfect funnel formed by their divergence. They re- solve themselves into six pairs of arms, for each one is branched from the basal joint, dividing into two equal and similar portions. Those nearest the mouth are the shortest, and each pair increases regularly in length to the most distant, which are the central pair when the hand is extended. Each division of each of this longest and most extensile pair comprises, in the specimen be- fore us, thirty-two joints, while the shortest consists of about ten, the intermediate ones being in proportion ; so that the whole apparatus includes nearly five hundred distinct articulations, a wonderful provision for flexi- bility, seeing that every joint is worked by its own proper system of muscles. Moreover, every separate joint is furnished with its own system of spinous hairs, which are doubtless deli- eate organs of touch, since it has been established that the hairs with which the shelly coate of Crustacea are studded, pass through the substance of the latter, and communicate with a pulpy mass, richly supplied with nerves, which lines the shell.* These hairs project at a more or less wide angle from the axis of the finger * Proc. Royal Society, ix. 215. 994 EVENINGS AT THE MICROSCOPE. like filament, and are graduated in length; and what is very striking, as illustrating the exquisite workman- ship of the Divine hand, the hairs themselves are compound structures; for under a_ high power they seem'to be composed of numerous joints—an illusory appearance probably, what look like joints being rather succes- sive shoulders, or projections and constrictions of the outline— while each shoulder carries a ». whorl of finer spines, lying near- \, ly close to the main hair, and < scarcely deviating from its gen- S==SN\ eral direction. This barbed Ne structure of the hairs is chiefly ~ seen towards their attenuated extremities. And now do you ask—What is the object of this claborate contrivance, or rather series of contrivances ? I answer—lIt is the net with which the fisher takes his food—-it is his means of living. You have seen that the animal has no power of pursuing prey: he is im- movably fixed to the walls of his castle which is im- movably fixed to the solid rock. He is compelled therefore to subsist on what passes his castle, and on what he can catch as he sits in his doorway and casts his net at random. You saw, also, with what a regular perseverance the casts were made ; and now that you have examined in detail the construction of the net, you are prepared to appreciate its fitness for the work assigned to it. KC AN oN HAND OF BARNACLC. BARNACLES. 225 Its extreme flexibility, produced by the number of its joints, enables the fingers of the hand, or the threads of the net (which you will) to stretch out or to curl up alternately, while the number of the divergent fingers enables the animal to grasp a comparatively large bulk of water in those curling organs. These, then, form a sieve ; the water passes through the interstices of the fingers, while the tiny atoms of solid matter, or the equally minute animalcules that constitute the food of the Barnacle, are sifted out, and detained by the fingers, which curling inward carry whatever is captured to the mouth. But see how greatly the perfection of the instru- ment is enhanced by the projecting hairs with which every one of the numerous joints is beset. These, standing out at right angles (or nearly so) to the direc- tion of the finger, meet their fellows from the joints of the next finger, and crossing their points, fill the inter- stices with an innumerable series of finer meshes,— meshes of such delicacy that it is next to impossible that any organized body inclosed in the given area should escape. But there is more in them than merely this minute and wide-spread ramification. They are, as we have seen, organs of touch; so that the net has not only the mechanical power of capture, common to an inanimate cast-net which a human fisher uses, but is endowed with the most exquisite sensibility in every part. The slightest contact of an animalcule in the inclosed water with one of those thousands of sensitive hairs, com- municates instantly an impression to the sensorium, and a consciousness of the fact to the Barnacle; who is thus, without doubt, alle with the quickness of 10* 226 EVENINGS AT THE MICROSCOPE. thought to close the fingers together at that part, and thus secure the victim. To make use of the prey thus secured, the Barnacle is furnished with a mouth, which can be protruded into a sort of wart, and is provided with a distinet lip bearing minute palpi, and three pairs of jaws, of which the two outer are horny and toothed, while the inner- most is soft and fleshy. Fixed and immoveable as the Barnacles are in their adult and final stage, they have passed by metamor: phosis through conditions of life in which they were active roving little creatures, endowed with the power of swimming freely in the wide sea. In this condition they present the closest resemblance to familiar forms of Crustacea, as you will perceive when you examine some specimens of the larve that I am able to show you. I have in one of my tanks an individual of the fine and large Barnacle, Balanus porcatus, which for sev- eral days past, has been at intervals throwing out from the orifice of its shell dense clonds of atoms, which form compact columns reaching from the animal to the surface of the water. One of these cloudy columns, when examined with a lens, is seen to be composed of thousands of dancing creatures resembling the Water-fleas that we lately examined. They main- tain a vivacious motion, and yet at the same time keep their association and the general form of the column. Taking out afew of the dancing atoms, and isolat- ing them in this glass stage-cell, we see that they have exactly the figure, appearance, and character of the young of the common Cyclops, so that you would, BARNACLES. 935 without hesitation, if you knew nothing of their pa- rentage, assign them to that well-known genus. Their movements are almost incessant, a series of jerking progressions performed by quick but apparently labo- rious flappings of the limbs, right and left together. They occasionally rest from their exertions for a few moments, but seem to have no power of alighting on any object. But in order to obtain a more precise idea of the structure of this tiny creature, we must manage to restrain its liberty a little, by applying gentle pressure with the compressorium, just sufficient to confine it without hurting it. The body is inclosed in a broad carapace, shaped much like a heraldic shield, but very convex on the back, and terminating behind in a slen- der point or spine, which is cut into minute teeth along the edges. Below this shield is seen the body, with three pairs of legs, a great proboscis in the middle pointing downwards and backwards, and the anal fork, which consists of a bulbous base and two diverging points, which project behind under the spine of the shield. The legs are exclusively swimming organs; they have no provision for grasping, no claws or hooks, nor do they appear to be capable of being used for crawl- ing on the ground or for climbing among the sea-weeds. They are fringed along one edge with long and stout, but somewhat flexible spines, of which those that are nearest the trunk seem more rigid, and are directed more at right angles to the limb than the rest. The legs are formed of many imperfect joints, and the second and third pairs are double from the basal joint outwards, while the first pair are simple. In the fore 928 EVENINGS AT THE MICROSCOPE. part of the body a large eye is placed, deep-seated, which is of a roundish form, and is intensely black, both by reflected and transmitted light. On the sum- mit of the forehead are placed a pair of thick flexible horn-like organs, which are abruptly bent in the mid- dle, and which I believe represent the first pair of antennee. This then is the first stage of the Barnacle, —the form under which it appears when it is hatched from the egg. Among the multitudes which have been evolved during these last few days, and which are now swim- YOUNG OF BARNACLE. ming at large in the tank, we may be able to detect some that have passed through their first stage, and having moulted their skin have attained a more ad- vanced form. Jere is one, which by its superior size seems to have made some progress towards maturity. Yes, here are more. These are evidently in their BARNACLES. 229 sezond stage. ‘There is an increase in length; for whereas the former was only ;},th of an inch in length, these have attained to a length of ;';th of an inch. Yet this increase is observable in no other dimension than that of total length, and this is due to the devel- opment of the terminal spine of the shield, which is now much produced, and cut into minute teeth. The anal fork is also attenuated, lengthened, and bent abruptly downward at the base, where it is very mo- bile ; another bend in the middle throwing the extrem- ity into the horizontal again. The delicately mem- branous pouch-like proboscis is more-clearly seen be- neath the breast, the extremity of which is directed backwards. In front of this organ there are two de- curved very mobile bristles, set on pedicles, the whole closely resembling the internal antenne in the higher Crustacea. The lateral horns or external antennze ’ appear to terminate in a very delicate brush of hairs, which does not seem to be protrusile. The little animals in this state swim, generally, back downward; though they frequently assume a perpendicular position, both direct and reversed. I see them now occasionally resting on sea-weeds and Diato- macee, though the limbs seem even worse fitted than before for crawling, since the spines or bristles with which they are fringed are much increased in length, especially on the third pair. A specimen nearly twice as large as this last affords us an opportunity of tracing the Barnacle to another point of its transformations. The modifications are chiefly in the proboscis and the anal fork. The former now points directly downwards, is furnished with a pair of minute spines on its anterior side, and with a 230 EVENINGS AT THE MICROSCOPE. terminal hook; while its posterior side is set with strong vibrating cilia. The anal fork is greatly in- creased in dimensions, has its edges armed with spines articulated to its surface, and is marked with longi- tudinal lines which resemble corrugations. The under- surface of the body is also much corrugated trans- versely. In the first moult the spine of the shield was greatly increased, the size of the body itself remaining station- ary; in the seond moult the ratio is reversed, the body has largely increased, but the spine is nearly in statu quo. We cannot follow the metamorphosis any farther by personal observation, but from the researches of others, and especially of Mr. Darwin, we know that other stages have to be passed before the final fixed condition is attained. As yet no appreciable advance has been made, by either of the two moultings which we have traced, from the free, jerking, dancing Water- flea that was first hatched, towards the sessile Bar- nacle inclosed in its shelly cone of several valves, and firmly fixed to the solid rock; and we are yet at a loss to imagine how such a change can be ef- fected. Nor is the matter apparently helped by the next moult ; for though there now ensues a great change of form, it does not seem to resemble the adult Barnacle much (if at all) more than before. If described with- out reference to its parentage, it would still be con- sidered an Entomostracous Crustacean, or Water-fiea, but removed to another Tribe. It represents, in fact, a Cypris ;* the body with its fringed limbs being now * See figure on page 209. BARNACLES. 231 included within two convex valves, like those of a mussel or other bivalve shell, either united by a hinge along the back, or rather soldered together there, so as only to allow a slight opening and closing by the elas- ticity of their substance. The fore part of the head is now greatly enlarged, as are also the antenne, which project from the shell. The single eye is separated into two, which are large and attached to the outer arms of two bent processes which are placed within the body, in the form of the letters UU. The legs are increased by the addition of two pairs, and these are doubly bent in a zig-zag form, and can be protruded from be- tween the valves. It isa highly curious fact that the infant Barnacle has thus passed through two distinct types of animal life, the Cyclops and the Cypris. These are not one type in different stages, as might be reasonably pre- sumed. The young of Daphnia and of Cyclops are so much alike, that it would be natural to presume the young of Cypris to be of the same form; in which ease, we should have in the young Barnacle merely the first and second stages of Cypris. But it is not so. Cypris does not pass through the Cyclops form at all; for, according to Jurine, the young when hatched have the appearance of the perfect animal, though varying a little in the shape of their shells. It is in this second form, which may be considered the pupa of the Barnacle, that the animal quits its free roving life, and becomes a fixture for the remainder of its days. And this is a most wonderful process; so wonderful, that it would be utterly incredible, but that the researches of Mr. Darwin have proved it incontest- ably to be the means by which the wisdom of God has 932 EVENINGS AT THE MICROSCOPE. ordained that the little Water-flea should be trans- formed into a stony Acorn Barnacle. Having selected a suitable place for fixing its resi- dence—such as those massive rocks which sustain the impetuous billows on our sea-worn coasts—the great projecting antennze manifest a new and unprecedented function. Glands situated at their base secrete a tena- cious glue, which, being poured out in great profu- sion, cements the whole front of the head to the rock, including and concealing the antennz themselves. The cement rapidly sets under water, and the animal is henceforth immovable. Jt now moults its skin once more. Another great change takes place ; the bivalve shell is thrown off, as are also the eyes with their bent supports, and it is seen to be a true Barnacle, though as yet of minute dimensions, and with its valves in a very rudimentary condition. It is now the representative of a third type among the Crustacean forms, for it is in effect a Stoma- pod; such as the Opossum Shrimp (J/yszs), for ex- ample, with the shield composed of several pieces, stony in texture, on account of the great development of their calcareous element, and so modified in form as to make a low cone the legs (become the czrrz, or what I have above called the “ fingers”) made to perform their movements backwards instead of forwards, and the whole abdomen reduced to an almost invisible point. Marvellous indeed are these facts. If such changes as these, or anything approaching to them, took place in the history of some familiar domestic animal—if the horse, for instance, was invariably born under the form of a fish, passed through several modifications of BARNACLES. 933 this form, imitating the shape of the perch, then the pike, then the eel, by successive castings of its skin ; then by another shift appeared as a bird, and then, elueing itself by its forehead to some stone, with its feet in the air, threw off its covering once more, and became a foal, which then gradually grew into a horse 3 —or if some veracious traveller, some Livingstone or Barth, were to tell us that such processes were the in- variable conditions under which some beast of burden largely used in the centre of Africa passed,—should we not think them very wonderful? Yet they would not be a whit more wonderful in this supposed ease than in the case of the Barnacle, in whose history they are constanily exhibited in millions of individuals, and have been for ages,—even in creatures so common that we cannot take a walk beneath our sea-cliffs, without treading on them by hundreds! BR4 EVENINGS AT THE MICROSCOPE. CHAPTER XII. SPIDERS AND MITES. Spiers, I am sure, are not favourites with you With the exception of the poor prisoner in the Bastile, who had succeeded in taming a Spider—the only crea- ture besides himself that inhabited his dungeon—I do not think I have ever heard of any one who loved or admired Spiders, morally. Yet, physically, we may tind much to admire in them, as not a few naturalists have done before us; there are men who have devoted their lives to the study of this unamiable race, and who have discovered in them the same wondrous skill, and the same perfect adaptation of organ to func- tion, of structure to habit, that mark all God’s works, whether we think them pretty or ugly, amiable or re- pulsive. I am going to show you some of these pieces of mechanism. Jtemember that the whole tribe is sent into the world to perform one business,—they are com- missioned to keep down what would otherwise be a “ plague of flies.” They are fly-butchers by profession ; and just as our beef- and mutton-butchers have their slaughter-house, their steel, their knives, their pole-axe, their hooks, so are these little slaughterers furnished with nets and traps, with caves, with fangs, and hooks, SPIDERS AND MITES. . 235 and poison-bags, ready for their constant work. They haye, in fact, nothing else to do: their whole lives are spent in slaughtering—with the exception of rearing fresh generations of slaughterers—and I suppose they think, and are intended to think, of nothing else. I was one day in an omnibus, in the corner of which sat a butcher. Presently a man got in, whose blue gingham coat indicated the same trade. He seated himself opposite the other, and the two were soon in conversation. ‘Do you know Jackson?” says th of an inch in length when extended, though from its extreme ver- satility it is as difficult to assign to it a definite size, as a definite shape. It seems to be the £: sanguinea, so called because it is said to occur sometimes of a deep red hue, and in such vast profusion, as to give the waters the appearance of blood. I have never seen it, nowever, other than as it now appears, rich emerald green in the body, with the two extremities perfectly INFUSORIA. 445 clear and colourless. I might perhaps describe ite ordinary form as spindle-shaped, with a pointed tail, and a blunt, rounded head; butit is remarkable for the variableness of its shape. It is capable of assuming an appearance very diverse from what it had half a minute before, so that you would hardly identify it, if you were not watching its evolutions. Whether this ability to prove an adzas be at all dependent on the remarkable clear-headedness of the subject, I leave for you who are skilled in metaphysics to determine. Away they go tumbling over and over, revolving on the long axis as they proceed, which they do not very rapidly, with the blunt extremity forward. Here is another form, a little larger than the former, but much more slender; yet from the slowness and steadiness of its movement more easy of observation. It is named £. acus, or “ the Needle Euglena.” This is an animalcuie of great elegance and brilliance; its sparkling green hue, with colourless extremities, and its rich pale crimson eye, are very beautiful. It commonly swims extended, with a slow gliding motion, turning round on its long axis as it proceeds, as may be distinctly seen by the rotation of certain clear oblong substances in its body. These then are seen not in the interior, but near the surface, as they would appear if imbedded in the flesh around a hollow centre. The interior is probably not hollow, but occupied with pellucid sarcode. These were assumed by Ehrenberg, but on no adequate grounds, to be organs connected with reproduction. They vary in number in different individuals, and those which contain the greatest number are thereby more swollen. They appear to be separated into two series, one anterior, the other posterior. The animal is 446 EVENINGS AT THE MICROSCOPE. capable of bending its head and body in varions dizee tions, but is most beautiful when straight. The front is furnished with a slender thread-like proboscis. This species affords us a good opportunity of observing the red spot which, for ¢onvenience sake, we may still term an eye. It seems to be an irregular oblong vacuole, or excavation in the sarcode, filled with a clear ruby-red fluid. The red spot in the Lotzfera is connected with a well-defined crystalline lens, whose definite form, and high refractive power, may in many cases be distinctly marked; but here nothing of the kind is seen; the spot itself has no certain shape, and does not appear to be bounded by a proper wall. Some forms, which are by general consent admitted to be plants, have similar spots; and hence it has been, rather too hastily, I venture to think, concluded, that they can have no connexion with vision. I think it still possible, that a sensibility to the difference between light and darkness may be the function of the organ. I have found that this animal, when allowed to dry on a plate of glass, retains its form and colour pertectly ; but in about two days the eye-spot, which at first be- comes much larger in the drying, gradually loses all traces of its brilliant colour, probably by the evapora- tion of the contained fluid. Another pretty species you see gliding along amongst the rest, called Z. triqguetra, or the Three-sided. It bears a resemblance to a broad rounded leaf, with the footstalk forming a short transparent point, and the mid-rib elevated into a sharp ridge. The under side seems slightly concave. This is equally attractive with the others. It is persistent in form, and appears not to be even flexible. Its motion is slow, and as it goes, INFUSORIA. 447 it rolls irregularly over ‘and over in all directions, not revolving on its long axis, and thus giving you very satisfactory views—though only momentary—of the keel with which the back is furnished. It is in the turnings of such minute creatures that the microscopist often gets a glimpse of peculiari- THREE-SIDED EUGLENA. ties of form, which a view of the animal when in repose, however long continued, fails to reveal. Longitudinal interrupted lines are seen running down the body of this pretty leaf, which do not appear to mark irregularities of the sur- face, and therefore are probably internal. Ehrenberg ealls these and similar collections of granules “ ova,” or eggs; but this is to eut the knot, instead of untying it. There is no sufficient reason to believe that these animals increase by ova. About the front of all these Luglene, you may discern now and then a slight flickering or quivering in the water. The power we are using, though best for the general display of the form, is insufficient to resolve this appearance: I will put on a higher objec- tive. You now sce that there proceeds from the frontal part of the body, along and very slender filament, which is whisked about in the manner of a whip-lash. This is considered to be the organ of locomotion; but I rather doubt that such is the function; the smooth and even gliding, often rotating, of the creature, seems more like that produced by minute and generally distributed cilia, than that caused by the lashings of a single long thread. Yet two more species of this extensive genus we 448 EVENINGS AT THE MICROSCOPE. discern in this well-stocked drop of water. They have received the appellations of the Pear (2. pyrum), and the Sloth (Z. deses). The former is the most minute we have yet seen, and seems to be scarce; but it is highly curious and interesting in appearance. It much resembles, in outline, a fish of the genus Balistes ; the muzzle being somewhat protruded and truncate, and the form rhomboidal; it terminates in a slender pointed tail. The body is obliquely fluted, which gives a very singular effect; for from the transparency of the tissues the lines of the opposite side can be discerned crossing those next the eye, and dividing the animal into lozenge- shaped areas. The colour is sparkling green, but the tail and the edges of the body are clear and colourless: and there is a bright red eye. At other times this Luglena takes the form of a claret-bottle, or an oil-flask ; the muzzle being broadly truncate, or even indented. Its motion is rapid; a swift gliding in the direction of its long axis ; it turns continually on the same axis, which gives a waving irregularity to its course; and has a pretty effect from the continual crossing of the flutings in the revolving. This specimen is abont =45th of an inch in length, including the tail. Euglena deses is much larger, being about 31;th of an inchin length, thongh the tailis very short. It has a thick body ; with around blunt head ; it taperssuddenly to the tail. Its colour is bright green with a red eye; but the presence of an infinite number of irregular oblong granules and lines, with several globular vesi- cles, gives an opacity and a blackness to its appearance. In its manners it is sluggish ; it never swims or glides gracefully and swiftly among its playful congeners, but contents itself with twining slowly among the flocose ————— a INFUSORIA. 449 stems and filaments of the water-plants, or crawls upon the surface of the live-box. It does not appear to change its form, otherwise than its soft and flexible body necessitates, as it twines about. But enough of the Huglenas. For [have just caught sight of a still more curious creature, the Swan Ani- maleule (Zrachelocerca olor). It is reposing on one of the leaves of the Myriophyllwm, its long and flexible neck lengthening and contracting at pleasure, the tip thrown about in quick jerks, in every direction, some- what like a caterpillar when it touches several points impatiently with its head. If we admire the graceful sailing of a swan upon a lake, the swelling of its rounded bosom, the elegant curves of its long neck, we shall be struck with the form and motion of this animal. The form has much resemblance to that of a swan, or still more to that of a snake-bird (/Votus); the body, swelling in the middle, tapers gradually into a slender pointed tail, at one ex- tremity, and at the other, into a very long and equally slender neck, which is terminated by a slight dilitation. The whole is perfectly transparent, but the body is filled with numerous minute globular vessels, or tempo- rary stomachs. The grace of its motion as it glides along with a free and moderately swift progression through the clear water, or winds through the intricate passages of the green conferva, throwing its long neck into elegant curves, is very remarkable. There are, I see, two of them, which however take no notice of each other, even when passing close to each other; the neck of one is much longer than that of the other. Now and then, when gliding along, the neck is suddenly contracted, but not wholly, as if something had alarmed A50 EVENINGS AT THE MICROSCOPE. or displeased the animal: the body also can be swollen or lengthened at pleasure; it can move in either di- rection, but the neck usually goes foremost, extended in the direction of the motion, and seems to be used to explore the way. I had once an opportunity of seeing the process of increase by spontaneous self-division in this creature. It was an unusually large specimen, found in an old in- fusion of sage leaves. When I discovered it, it was darting about its long neck in the most beautiful con- tortions. As it was partly hidden by the vegetable fibres present, I partly turned the glass cover to alter the position of the contents. On again looking, the Swan was in a clear part of the field, but in the form of a dark globose mass, the neck being entirely con- tracted. It was quite still, except a continual slight alteration of the form by the protrusion or contraction of parts of the outline. The body seemed full of minute globules, set in a granular mass of a blackish hue, and SWAN-NECK AND ITS DIVISIONS. the outline was not a continuous line, but furmed a multi- tude of rounded elevations. Presently it protruded the clear neck, but only for a short distance, and then re- tracted it as before; when the only indication of the INFUSORIA. 451 presence of this organ was a depression in one part of the surface, somewhat like the mouth of a closed Acti- nia, where there was a slight but incessant working, very much like the irregular motion on the surface of’ boiling water, in miniature; there was also an indistinct ciliary action at this part, not of rotation, nor of vibra- tion, butasortof waving. Atthis point I had occasion to get up from the table, and thongh I was not away more than a minute, on my return I observed a strong constriction around the middle of the body. It was transverse, for the depressed and ciliated mouth was at a point exactly at right angles to the constriction. From the depth to which this latter extended in so few minutes, I supposed the process of separation would be very rapid; for I could very soon see a line of light all across at intervals, and the two halves seemed to slide freely on each other. Yet they remained long without much apparent progress, or even change, except that the anterior half at one time threw forth its neck a short distance; at this time it looked extremely like a bird, bridling up its lithe neck and swelling bosom; while to make the resemblance perfect, it began to imitate the action of a fowl picking up grain, bobbing its head hither and thither; so curious are the analogies of nature! Along the dividing line, there had appeared very early in the posterior half, a distinct ciliary action ; after a while (how, I do not exactly know) without the general relation of position being changed, the mouth of the anterior (which must now be called the old) animal appeared on the side, and at the point corres- pondent in the other, a similar ciliary wreath appeared, while the action along the dividing line was no longer seen. Sothat the division which was at first transverse 452 EVENINGS AT THE MICROSCOPE. now appeared longitudinal. I believe, however, the animals were really separated before this, though they remained in contact, for as they slid over each other, it was manifest that each had an independent action. At length, about an heur and a half after the first appearance of the constriction, the new animal threw out its clear neck to a great length, writhing it about with rapid agility, and forming the most elegant curves, like those of a serpent, often completely encir- cling its own body with it. It still remained, however, in contact with its parent, which, after a time, also protruded its neck in the same manner. Both then retracted and remained still for a while; and again, almost simultaneously, threw out their long necks, and again retired to sluggish repose. Among the sediment, the grains of which are driven hither and thither by their spasmodie jerking movements, you see several individuals of another sort of creatures—the Chrysalis Animaleule (Paramecium aurelia.) ‘This is a “whale among minnows;” for it is greatly larger than any of those we have yet ob- served ; and is just visible to the naked eye, when we hold up the live-box obliquely against the light; for then the animals appear as the smallest possible white specks. Bringing them again under the microscope, each presents a pellucid appearance, and an oblong figure, of which the fore part is somewhat narrowed. The hack rises in a rounded elevation; and the mouth is situated as far back as the middle of the body upon the under surface, where its position is marked by a sort of long fold, the sides of which are fringed with long cilia, whose vibrations are very marked. The INFUSORIA. 453 whole surface, on both sides, is covered with minute cilia, arranged in longitudinal rows, of which, accord- ing to the great Prussian professor, there are from thirty to sixty on each surface, each row bearing sixty or seventy cilia. This must be considered as an ap- proximation ; for we may well doubt the accuracy of the counting, when the objects are so very evanescent as these vibrating cilia. The vacuoles, and the temporary stomachs, more or less completely filled with the brown and green food, which the animals are collecting from the de- eayed vegetable matters, are sufficiently numerous and conspicuous; but they may be rendered still more so by the device of mixing a little carmine with the water. The ciliary currents are thus instantaneously rendered strikingly visible. The crimson atoms are attracted from all quarters towards the tail of the ani- mal, whence they are urged in a rapid stream along one side towards the head, around which they are hurled, and then down the other side to the tail, ponr- ing off in a dense cloud in a direction contrary to that in which they originally approached. But now the gathered currents have produced their expected result; for many of the globular vacuoles are already become of a beautiful rosy hue, from the mi- nute particles of the pigment which have been whirled to the mouth, and swallowed. The feature of greatest interest, however, in this animal is the contractile bladder. Two of these organs are usually seen co-existent in each individual; placed, the one on the front, the other in the rear of the mouth, but near the opposite—z. e. the dorsal, surface of the body; for as the creature slcwly revolves on its longi- A454 EVENINGS AT THE MICROSCOPE. tudinal axis, the line of the vesicles alternately ap- proaches and recedes from that of the mouth. They are remarkable for their structure. Far from the sim- plicity in which the organ is usually presented to us in the animals of this class, the contractile bladders are here very complex. Each when distended is globular; PARAMCCIUM. and it is surrounded by a number of others of much smaller dimensions, and of a drop-like form, so set as to radiate round the principal vesicle as a centre, the rounded portion of each in apparent contact with the vesicle; and the slender extremity running off as an attenuated point till lost to sight in the sareode. The main vesicles alternately become distended, and sud- denly contract to a point; while the radiating cells are continually varying in size, though in a less degree. It is customary to describe the secondary vesicles as coming into view at the instant of the contraction of the primary one, and to suppose that the emptying of the one is the filling of the other; but I have not been able to observe this mutual relation satisfactorily made out. The smaller as well as the larger vesicles are conspicuous from their colourless transparency; for the general sarcode of the body, though pellucid, is only so in the same degree as glass, slightly smoked ; besides that its clearness is often impaired by crowds of granules and minute globules. INFUSORIA. 455 You ask what is that comparatively large oval body attached by its side to one of the leaves of the plant. It is the egg of some considerable Rotifer, probably Euchlanis, which is always glued to some filament or stem of a water-plant. It may interest you to watch the progress of the contained embryo, which you can readily do, since the egg-shell is as transparent as glass, and the infant animal already displays the movements of independent life. Meanwhile I will tell you the tragical and lamentable history of just such an embryo as this, that was eaten up before it was born, under my own eye. One of the depredators was a very amusing animalcule, which is sufficiently scarce to make its oc- eurrence a thing of interest, especially to a young mi- croscopist, as I was at the time. A large egg of (as I believe) Luchlanis dilatata had been laid during the night on a leaf of JVzéella, in the live-box. When I ob- served it, the transpa- rency of the shell allow- ed the enclosed animal, to be seen with its vis- cera; which occasionally contracted and expand- ed ; the place of the mas- tax I could distinctly make out. The cilia were vibrating, not very rapidly, but constantly, on the front, where there was a vacant space between the animal and the shell. Irom 7 a. m., when I first saw it, 1 watched it for about eight hours, without perceiving any change; but at that hour, having withdrawn for a short time, I per- VY a bP COLEPS AND CHILOMONAS. 456 EVENINGS AT THE MICROSCOPE. ceived on my return that a portion of the animal was outside the shell. The appearance was that of a small colourless bladder oozing ont, at an imperceptible aperture; and this oval vesicle quickly but gradually increased, until it was half as large as the egg itself. A little earlier than this point, the cilia were seen on the front or lower side of the excluded portion, and these began to wave languidly in a hooked form. They thus seemed much longer and more substantial than when rotating in the perfect animal. When excluded to the extent just named, some little creatures that were flitting about found it, and began to assemble round it. These were far too rapid in their movements to allow me to identify them before, or to perceive any thing else than their swift motion and oval form ; but this attraction causing them to become still, allowed me to perceive their singular and beautiful structure. Each consists of an oval vase open at the top, the margin of which is cut into a number of little points ; the sides are marked by a series of ribs, which run down longitudinally, and are crossed by other trans- verse ones; the rounded bottom is furnished with three short points; so that the whole reminded me of a barrel with its staves and hoops, set on a three- legged stool. Within the body, which is colourless, are seen small dark spots, which are probably the stomach-vacuoles. Thus I identified these little bar rels with Coleps hirtus of Ehrenberg, but I found no record of their carnivorous propensities. One after another whirled into the field, and after a few gyra- tions became stationary at the head of the half-born Euchlanis, just as I have seen vultures gather one by one to a carcase. Very soon there were a dozen or —— INFUSORIA. 457 fifteen of them, some of which were ever shifting their places, and some were playing around, or revolving on their longitudinal axis. I found that their object really was to prey on the soft parts of the creature just excluded from the egg; for by carefully watching one, I distinctly perceived particles of the flesh fly off, as it were, and disappear in the body of the Coleps. The appearance was that of steel-filings drawn to a magnet, for the mouth of the Coleps was not in actual contact with the flesh; and therefore, I suppose, the surface having been ir some way ruptured (which I could see it was), the loose gelatinous atoms were sucked off by a strong ciliary current. They did not attack any other part, and after having continued their murderous occupation about ten minutes, they one by one departed. The ciliary motion of the Auchlanis ceased immediately after it was first attacked, and I suppose it was soon killed, for it did not increase in size in the least afterwards. When the Colepes left it, a great portion, perhaps a third, of the excluded parts, was devoured. As soon as the depredators were gone, or even before, others more diminutive, but more numerous, were ready to take their place. The drop of water under review had been found amazingly full of a small Monas, perfectly transparent, of an oval form, with some granules visible in the interior. They were about zoseth of an inch in length. They filled the whole field, gliding about very nimbly, but so close as but just to allow space for motion, and that in several strata. By the morning these were collected in masses, which, to the naked eye, looked like little undefined white clouds, but which under the microscope showed 20 458 EVENINGS AT THE MICROSCOPE. the Monads in incalculable multitudes, but for the most part in still repose. Some were still moving to and tro, however, and, in the course of the day, most of them became again active. As soon as the Colepes had forsaken their prey, the Monads began to gather around it, cleaving to the same parts, and apparently imbibing the juices; for the extruded parts still slowly decreased, until at length these were reduced to about one-third of their original dimensions. A close examination of these latter, when they had settled to rest, showed me that they were of the species Chilomonas paramecium. There is an indentation on one side of the front, where the mouth is situated ; here there is a ciliary action; the projecting part, called the dzp, is said to be furnished with two slender flexible proboscides; but my power was not sufficient to discern any trace of these. A sort of a ridge, or keel, runs down the length of the body, perceptible by a slight line; numbers of stomach cells also are per- ceptible. The motion of these lip-monads was not very rapid when unexcited ; it is performed by a sort of lateral half-roll, the two sides alternately being turned up, like a boat broadside to a swell, and the line of progression is undulating. And now having pretty well exhausted the con tents of this live-box, let us try a dip from this other phial from another locality, equally productive, if I am not mistaken. Yes; for, to begin, the stalks of Witella here are fringed with populous colonies of the most attractive of all the Infusoria, the beautiful Vorticelle. The species is not the common bell-shaped one, but the smaller with pursed mouth, the little V. micros toma. INFUSORIA. 459 Look at this active group, consisting of a dozen or so of glassy vases, shaped something like pears, or ele- gant antique urns, elevated on the extremities of long and very slender stalks, as slender as threads, and about six times as long as the vases. The stalks grow from the midst of the floccose rubbish attached to the plant, and diverge as they ascend, thus carrying their lovely bells clear of one another. Each vase is elegantly ventricose in the middle, terminating below in a kind of nipple to which the stalk is attached, and above in a short wide neck with VORTICELLE, a thickened rim. This last is highly sensitive and con- tractile; its inner edge is set round with a circle of vibratile cilia, which, when in full play, produce a pair of small circular vortices over two opposite points 460 EVENINGS AT THE MICROSCOPE. of the brim. The cilia themselves cannot be distin. guished, but their optical expression is curious. At the two opposite points of the circular margin, as seen in perspective when slightly inclined towards the ob- server, viz., at those points where the cilia, from their position with regard to the eye, would be crowded to- gether, there are seen two dark dashes, representing, doubtless, two ciliary waves, but which have all the appearance of tangible objects, sometimes withdrawn, sometimes protruded, and often vibrating with a rapid snatching movement. These vases are of the usual appearance in Infuso- ria. Their substance is the clear transparent colourless sarcode, but it contains within it more or less of the cloudy nebulous matter which we have been lately familiar with. There are several globular vesicles or vacuoles, some ready to imbibe colour from pigment, and others already occupied with brown food, while in each case we see, near the centre of the vase, a longish body of clear granular texture, which is called the nucleus, and which seems to play an essential part in the vital economy of the animal. The movements of a group such as that we are looking at are very sprightly and pleasing. The vases turned in all directions, some presenting their mouths, some their sides, some their bases to the eye; inclined at various angles from the perpendicular, and bending in diverse degrees upon the extremity of their stalks ; swaying slowly and gracefully to and fro, as driven hither and thither by the ciliary currents, and, above all, ever flying up and down within the length of their radius, as a bird when confined by a string ;—all these circumstances impart a charm to this elegant animal. —— ee eee Se a ee INFUSORIA. 461 cule, which enables us to look long at it without wea- riness. This last movement is peculiar, and worthy of a moment’s closer examination. The stalk, when ex- tended to the utmost, is an elastic glassy thread, nearly straight, like a wire, but never so absolutely straight as not to show slight undulations. The stalk when thus rendered tense by extension, is highly sensitive to vibrations in the surrounding medium; and as in the circumstances in which we observe the animals, such vibrations must be every instant communicated to the vessel in which they are confined, the stalks are no sooner tense than they contract with alarm. This depends on a contractile cord which passes throughout the entire length of the stalk, and which is distinctly visible in the larger species as a narrow band. We can scarcely err in considering this ribbon as a rudi- mentary condition of muscle, though we do not recog- nise in it some of the characteristic conditions in which we are accustomed to see it in higher animals. The contraction of the muscle is very sudden, ener- getic, and complete. With a rapidity which the eye cannot follow, the vase is brought down almost to the very base of the stalk. Then it slowly rises again, and now we see, what we could not discern in the act of contraction itself, that in that act the stalk was thrown into an elegant spiral of many turns, which at the ut- most point of contraction were packed close on each other, but which in the extending act gradually sepa- rate, and at length straighten their curves. In any stage of the extension, the sudden contact of the vase with any floating or fixed object apparently eauses alarm, and induces the vigorous contraction; 462 EVENINGS AT THE MICROSCOPE. but vibrations, even when so violent as those produced by tapping the stage of the microscope with the finger- nail, have no effect unless the stalk be tense, its own power of vibration being then only developed, just as a cord becomes musical in the ratio of its tension. It is not until we view these creatures with a good microscope that we acquire an adequate idea of their beauty: for myself, at least, it was so. I had seen en- gravings of many of the invisible animalcules, and had read technical descriptions ; but of their brilliant trans- parency, their sudden and sprightly motions, their gen- eral elegance and delicacy, and the apparent intelli- gence with which they are endowed, neither books nor engravings had given me any conception. Some of the individuals under our present exam- ination are exhibiting phenomena of no less interest than their form and motions. Some of the stalks are terminated by ¢wo vases instead of one, which appear to spring from a common point. These, however, are the result of the spontaneous splitting of one; and in other examples you may see the process in different stages, or, if your patience endure a couple of hours’ watching, you may trace the whole phenomena, as I have done, from the moment when it first becomes re- cognisable, to its completion in the freedom of one of the newly formed animalcules. For instance, you perceive that one of the bells instead of being vase-shaped, has assumed a globular form. By keeping your eye on this for only a few moments, you detect a depression forming in the midst of its front outline, which momentarily deepens, until it is manifestly a cleft. The division proceeds down- wards, the two halves healing simultaneously, so that yy, '°*, Vy TT ee INFUSORIA. 463 they are at all times perfectly smooth and rounded; at length two vases appear, side by side, where a few minutes before there had been but one. One of these is destined to be ultimately thrown off, while the other retains sole possession of the stalk. You soon see which it is that is going to emigrate: for though the two are alike in size, the roving one early closes the mouth of the vase, becoming smooth and globular there, never to open again. The cilia, now therefore become useless, disappear by absorption ; but meanwhile a new circle of these organs are developed around the basal extremity of the “vase, and these, every instant becoming more vigorous in their motions, sway the little globe about on its point of attachment. At length the connexion yields, breaks, and the ani- maleule shoots away, rowed by its hundred oars, to find a new abode, and to found a new colony. Here and there you see shooting through the group, with a rapid gliding movement, an oblong clear body. This is one of the vases, formed by self-division, and exercising its newly found power of locomotion. It is giddily roving hither and thither, until the instinct of wandering ceases, when it will soberly settle down, affix itself by the point which was formerly its mouth, whence a new stalk will gradually grow, and opening a new mouth in the midst of the new crown of cilia. I believe that the division is sometimes transverse instead of longitudinal, the cleft occurring by constric- tion across the middle of the vase; but this I have not seen. In whatever direction it takes place, it is essen- tial that the oblong granular body, called the nucleus, which you see in each vase, be divided, the clett pass- ing through the middle of this substance, a portion 464 EVENINGS AT THE MICROSCOPE. of which is therefore appropriated to each new made animal. . That the essential vitality of the creature resides in this nucleus is shown by another and highly curious mode of increase, namely, that which is effected by encystion. Let us search the live-box carefully, for amidst so great a profusion of Vorticelle as we have ACINETA, on this 2V7tel/a, it will go hard if we do not find some individuals in the encysted stage. Look at this elegant object. It resembles a trum- INFUSORIA. 465 pet of the clearest glass, with a rounded extremity, and ‘with the bese affixed to the weed, from which it stands up erect. Within the expanded part of the trumpet there is a turbid mass, with a perfectly defined outline, from several points of which proceed radiating pencils or tufts of long, straight, stiff, elastic filaments, like threads of spun glass, varying greatly in length, and each terminated by a little knob of the same material. The tout ensemble of this object is very attractive and beautiful, and its history is a tale of marvels. No wonder that Ehrenberg, supposing this form to be an independent animal, gave it a generic and spe- citic name. He called it Acineta mystacina. For who would have suspected that this stiff and motionless ob- ject, with its tufts of flexible but inanimate threads, had any connexion with the sprightly vases which we have been examining? Yet it is the same animalcule, in what we may, with a certain liberty of phrase, call its chrysalis condition ! The history of the Vorticella, as it has been elabo- rately worked out by Dr. Stein, exhibits phenomena analogous to those marvellous changes which we lately considered under the appellation of the Alternation of Generations. Large individuals withdraw their circle of cilia, close up the mouth, and become globular, and then secrete from their whole surface a gummy substance, which hardens into a spherical transparent shell, inclosing the Vorticella in its cavity, in the form of a simple vesicle. Within this vesicle is seen the band-shaped nucleus, unchanged, and what was the contractile bladder, which, however, no longer con- tracts. By and by this torpid Vorticella enlarges itself ir- 20* 466 EVENINGS AT THE MICROSCOPE. regularly, pushing out its substance in tufts of threads, and frequently protruding from one side a larger mass, which becomes an adliering stalk. Thus it has become an Acineta, such as we now behold. From this condition two widely different results may proceed. In the one case, the encysted Vorti- cella separates itself from the walls of the Acineta, con- tracts into an oval body, furnished at one end with a circle of vibratory cilia, by whose moveinents it rotates vigorously in its prison, while the more obtuse end is perforated by a mouth leading into an internal cavity. In the interior of this active oval body there are seen the band-like nucleus, and a cavity which has again begun to contract and to expand at regular intervals. It is, in fact, in every respect like a Vorticella vase, which has just freed itself from its stalk. Presently, the perpetual ciliary action so far thins away the walls of the Acineta that they burst at some point or other, and the little Vorticetla breaks out of prison, and com- mences life afresh. The Acineta, meanwhile, soon heals its wound, and after a while develops a new nucleus, which passes through the same stages as I have described, and bursts out a second Vorticella. But the cycle of changes may be quite different from this. For sometimes the nucleus within the Acineta, instead of forming a Vorticella, breaks itself up into a great number of tiny clear bodies, resem bling Monads, which soon acquire independent mo- tion, and glide rapidly about the cell formed by the inclused Vorticella-body as in a little sea. But by and by, this body, together with the Acineta wall, suddenly bursts, and the whole group of Monad-like embryos are shot out, to the number of thirty or up- —_ Ce ee ee, ee ee INFUSORIA. 467 wards. The Acineta now collapses and disappears, having done its office, while the embryos shoot hither and thither in newly acquired freedom. It is assumed, on pretty good grounds, that these embryos soon be- come fixed, develop stalks, which are at first not con- tractile, and gradually grow into perfect Vorticelle small at the beginning, but capable of self-division, and of passing into the Acineta stage, and gradually attain- ing the full size of the race. Some forms of the same family, Vort¢cellada, are interesting as dwelling in beautiful crystalline houses, of various shapes, always elegant. All these have been ascertained to pass through the same or similar Acineta stages. Cothurnia imberbis is one of the prettiest of these. The cell is of an elegant ampulla- like form, perfectly transparent and colourless, set on a stiff foot, or short pedicle, which shows many trans- verse folds, like those of leather. From the mouth of the vase projects the animal, whose form may be dis- tinctly traced through the clear walls of the cell, at- tached to its bottom, whence it stretches upward when seeking prey, or to which it shrinks when alarmed. In the former condition the body resembles a much elongated Vorticella, with a similar circular orifice, set round with cilia. Often the animal performs its ciliary vibrations within the shelter of its house, not venturing to protrude beyond its rim. If carmine be mixed with the water, the atoms are seen in the customary vortex, and some are occasionally drawn into the cell nearly half-way down its cavity, and then swiftly driven out again. On a slight tap upon the table the animal withdraws, and in the same moment the urn bends down upon its leathery pedicle, at a point where there 468 EVENINGS AT THE MICROSCOPE. is always an angle, until the rim of the cell is in con- tact with the plant to which it is attached. This action is instantaneous. Presently, however, it rises, and re- sumes its former position, and then the mouth of the cell slowly opens, and the animal again protrudes, the cilia appearing first, and finally the head or front part of the animal, which is then opened and begins to rotate. Very similar to this are the Vaginicole, but the cells which they inhabit are not stalked, but are im-— movably affixed to plants. In V. erystallina, the cell is a tall goblet, standing erect, perfectly colourless ; while in V. decumbens, it is slipper-shaped, attached along its side, and of a golden-brown hue, but still quite transparent. Here is, fortunately, a group of the latter species, scattered about the leaves of the Nitella. Though, in general, both in form and _ habits, closely like the Cothurnia, yet the Vaginicola has VAGINICOLA. some peculiarities of interest. The cilia are more de- veloped, and can be more distinctly seen than in either Cothurnia or Vorticella, forming, when in swift action, INFUSORIA. 469 a filmy ring above the margin, along which, as if upon a wheel, one or more dark points are frequently seen to run swiftly round; the optical expression, as I pre- sume, of a momentary slackening in the speed of the wave. The act of seli-division takes place in this animal, as in the Vorticelle ; and it is curious to see two Vayinicola, exactly alike, lovingly inhabiting the same cell. One of the cells which we are now exam- ining is in this doubly tenanted condition. I will now exhibit to you some examples of the most highly organized forms of this class of animals, in which we discern a marked superiority over any that we have yet looked at, and a distinct approach to those animals whose more precise movements are per- formed by means of special limbs. These creatures are excessively common, both in fresh and sea water, wherever vegeiable matter is in process of decomposi- tion ; and hence their presence can at all times be com- manded by keeping infusions. In this old infusion of sage leaves for instance, they occur in vast multitudes, past all imagination; as you may see with a lens in this drop. This group belongs to the genus Stylonychia, and I believe to the species S. pustulata. It presents the form of an oval. disk, which, when seen sideways, is found to be flat beneath and convex above. It com- monly swims with the belly upwards, and when ex- hibited on the stage of the microscope, in almost every case, this surface is presented to the eye. It darts about very irregularly, with a bobbing motion, rarely going far in one direction, but shooting a little dis- tance, and then instantly receding, turning short round, and starting hither and thither, so fitfully that it is very 470 EVENINGS AT THE MICROSCOPE difficult to obtain a fair sight of its structure. Its mar- gin, however, 1s surrounded by short cilia; the mouth, which is along opening on the front part, and at the lett side (as to the animal) of the ventral surface, is fringed with long cilia, which are continually vibrating. These are the organs of the darting motion; but the creature crawls like a mouse, along the stems of con- ferva, &e., which it performs by means of curved spines, called wneini, near the front part, the points of which are applied to the stem, and also by long stiff styles, or bristles, which project backward and downward from the hinder part. Sometimes the animalcules crawl for a moment back-downward, on the inner surface of the glass cover, when the bases of the anterior curved spines appear dilated like large spots. The spines are not capable of much action, but they are rapidly used. The general appearance of the creature reminds us of the little Wood-louse or Armadillo of our gardens. The interior of the body is occupied with a granular sub- stance, in which are scattered many globular, vesicles of different sizes. The animal is very transparent, and almost colourless. They increase very tast by trans- verse division, which is performed under the micro- scope, so as greatly to increase the number under ex- amination, even in an hour or two. A constriction forms in the middle of one, which quickly deepens, dividing the oblong creature into two of circular figure. The mouth of the new one, with its vibratile cilia, is formed long before separation is complete, and at the same end and side asin the parent. The styles and bristles then form, and the creatures are held together for a few secords by these organs, even when the INFUSORIA. 471 bodies are distinctly severed. When separated, they retain the round form tor some time. When a drop of water is examined between two plates of glass, it is amusing to observe the numbers that congregate in the sinuosities left by the gradual drying of the fluid. This probably becomes unfit for respiration, for the motion of the cilia becomes more and more languid, and the creatures die before the water is dry. They not only die but vanish, so that where there were scores, so close that in moving they indented each other’s sides and crawled over one another—if we look away for a few minutes, and again look, we see nothing but a few loose granules. This puzzled me, till I watched some dying, and I found that each one burst and as it were dissolved. The cilia moved up to the very last moment, especially the strong ones in front, until, from some point in the out- line, the edge became invisible, and immediately the animal became shapeless, and from the part which had dissolved the interior parts seemed to escape, or rather the skin, so to speak, sceined to dissolve, leaving only the loose viscera. From the midst of these then pressed, as if by the force of an elastic fluid within, several vesicles of a pearly appearance, varying in number and size, and then the whole became evanescent. You will have observed that the admixture of car- mine to the water, while the animalcules were active, shows the direction of the ciliary motion with great distinctness. The particles form two vortices, one on each side of the front, which meet in the centre ina strong current, and pass off behind the mcuth on each side. We do not perceive that any of them swallow 472 EVENINGS AT THE MICROSCOPE. the partic.es of carmine, for the internal vessels remain colourless. I have found that if a drop of water containing these animals, be placed on a slip of glass exposed to the open air, they do not burst as the water dries away ; but dry flat on the glass, their bodies broader, but shorter than when alive, and quite entire. Their cilia are then very manifest. On being again wetted, though after only a few minutes’ desiccation, I have never been able to revive them, nor any other Jnfu- sorta in like circumstances, notwithstanding what is stated in books. Here is another species in equally amazing pro- fusion, S. mytilus. Its form is oblong, with rounded extremities, the anterior obliquely dilated. This spe- cies affords a good example of the various organs of locomotion. A transparent oblong shield, which is quite soft and flexible, is spread over the back, which does not prevent the eye discerning all the organs through it, thongh much more commonly the animal, when under the microscope, crawls belly-upward, beneath the glass cover of the live-box. Around the anterior part, which is broadened, are placed cilia, which are vibratile; these are continued round the mouth, a sort of fold on the side. Towards the posterior extremity on each side are other rows of cilia, which being large are well displayed. On the ventral surface, chiefly towards the front part, are seen several thick pointed processes, shaped like the prickles of a rose, but flexible, and capable of being turned every way. These are the wneind, and are evidently used as feet, the tips being applied tothe glass. The optical effect of the throwing about of these wncin?, when the place — -— csi Nailin stitial ae. aes INFUSORLIA. 473 which they touch is in focus, is very curious. They are rapidly moved, but without regularity; the tips bend as they touch the surface of the glass; some of them seem to have accessary hairs, equally long, but slender, proceeding from the same base. On tlie hinder quarter of the ventral surface are several thick pointed spines; these are inflexible, nearly straight, placed side by side, but not in regular order, some reaching beyond others. I have not seen these used, but they commonly remain sticking out in a horizontal direction. These organs are termed styles. Besides these, there are three slender bristles, called sete, placed at the hinder extremity, the central one in the line of the body, the others radiating at an angle. These are distinguished from the cilia, not only by their length, but by not being vibratile. The motions of these animals are powerful, but irregular and fitful, very much like those of the former species. They dart hither and thither, backward as well as forward, oc- easionally shooting round and round in a circle, with many gyrations, much like the pretty little polished beetles (Gyrinus) that play in mazy dances on the surface of a pool. The two extremitics seem covered with minute pits or stipplings, but colourless ; the central part is occupied with yellowish granules of different sizes. I once witnessed the dissolution of one of these animals under peculiar circumstances. Two or three stems of an aquatic plant had become crossed in the live-box so as to form an area, into which the Stylony- chia had somehow introduced himself. There was just room for him to move backward and forward without turning, and the space was about three times his own 474 EVENINGS AT THE MICROSCOPE. length. Within this narrow limit he impatiently con- tinued crawling to and fro, moving his uncini with great rapidity and showing their extreme flexibility, for as he applied them now to the stem, now to the surface of the glass, these whip-like uncini were some- times bent donble. The so-called styles at the posterior extremity, though less frequently used so, were yet occasionally bent and applied to the surface as feet, so that they are certainly not inflexible as supposed, nor do I see any essential difference between them and the uncini. The whole body was flexible, taking the form of any passage or nook into which it was thrust, yet recovering its elasticity immediately the pressure was removed. Its proper form appeared to be convex above and coneave beneath, rather than flat. After having been thus employed about half an hour under my observation, it became still, moving only its cilia, when I left it a little while, and on my return found that it was dissolved; the outline having en- tirely disappeared, and nothing being left but the granules, and globular vesicles, that had constituted its viscera, some of which still contained the carmine which had been very perceptible in the living animal. This was the more remarkable as there was plenty of water. It looked like suicide, a spontaneous choosing of death rather than hopeless captivity. Common as these Stylonychie are, and abundant beyond all calculation, where they do occur, from their tendency to self-division, they are not so univer- sally met with as their cousins, of the genus Luplotes. These are still more highly organized, and will please you by their activity and sprightly intelligence, I am sure. Here are several individuals in the live-box at this moment. ——? INFUSORIA. 475 They differ from the Stylonychia, in having the soft body covered with a plate of crystal mail, hard and inflexible, much like the shield of a Tortoise. Several species have this glassy shield marked with delicate lines running lengthwise; sometimes in the form of parallel ridges, as in a little species found in infusions (perhaps £. charon ;) at others forming rows of minute round knobs, as £. truncatus, the species now before us. The shield is ample, considerably overlapping the soft body ; it rises into an arched form in the centre; and is more or less round or oval. The mouth is ob- lique, and extends a long way down the under sur- face; it is set with strong and fine cilia, which also spread over the front. The organs of motion are, as before, long styles, pointed and rather stiff processes, which project from beneath the shell backwards and downwards, and soft hook-like uncini which are set chiefly near the fore part of the inferior surface. In the species before us, these are about six or seven in number, but in & charon they are more numerous. The twinkling rapidity with which these little feet are applied to the surface in crawling affords a pleasing sight; particularly when the animal is running back-downwards on the upper glass plate of the live-box. Some species have bristles (or sete) affixed to the hinder part of the shell, from which they diverge. In £ truncatus these are four, but they are wanting in Z. charon. The body displays a mass of granules, vacuoles, and vesicles of different sizes. EUPLOTES. 476 EVENINGS AT THE MICROSCOPE. These are very beautiful objects; and then sprightly motions, and apparent intelligence, give them an additional interest. They crawl more than they swim, running with great swiftness hither and thither, frequently taking short starts, and suddenly stopping. The specimens which we are examining are taken from water which had been kept in a jar for several weeks. The vegetable matters are decaying, and among the stems and filaments this pretty species crawls and dodges about. It seems reluctant to leave the shelter of the decaying solution ; sometimes one will creep out a little way into the open water; but in an instant it darts back, and settles in among the stems and floceu lent matter. Any attempt by turning the glass cover to bring it out into view only makes it dive deeper into the mass, as if seeking concealment. This is about zisth of an inch in length of lorica; and the E charon is not more than one-fourth of this size. These crea- tures remind one of an Oniscus, especially when in profile. There is an animal very closely allied to these, but much more beautiful, being of a clear greenish trans- Incency, with several vesicles filled with a rose- coloured or purple fluid of much brillianey. This creature, which bears the name of Chlaimidodon, has the peculiarity of a set of wand-like teeth arranged in a hollow cylinder. And with these we dismiss the Jnfusoria, a class of animals, which, from their minuteness, the number and variety of their species, their exceeding abundance, the readiness with which they may be procured, and, as it were, made to our hand (by simply steeping vegetable matter in water, and the uncertainty which still pre: ee ee a a 1 Se INFUSORIA. 477 vails as to many parts of their structure and economy ; and therefore, as to their true affinities in the great Plan of creation—offer one of the most promising fields of research which a young microscopist could eultivate. These are thy glorious works, Parent of good Almighty ; thine this universal frame ; Thus wondrous fair; Thyself how wondrous then! Unspeakable, who sitt’st above these heav’ns, To us invisible, or dimly seen In these thy lowest works ; yet these declare Thy goodness beyond thought, and power divine. [INDEX Acineta, 464, Acoutia, 410. Air-tubes of Fly, 107. Aleyonium, 899, Alternation of Generations, 374, 584. Ameba, 433. Anchors of Synapta, 345. Animalcules, 444. Antenne of Chafer, 187. Crab, 197. Fly, 191. Gnat, 192. Insects, 184, Moths, 188. Skipjack, 188 Weevil, 185, Aphrodite, "303. Arcella, 437. Barnacles, 221. hand of, 223. transformations of, 226. Bee, eyes of, 196. foot of, 136, mouth of, 163. sting of, 142. wing of, 82. Beetle, mouth of, 160. “ Bird’s-head,” 7: 2, use of, 7. Blood of Beasts, 29. Birds, 30. Fishes, 30. Frog, 81. #= Man, 29. Reptiles, 30. Tvnicate, 36. Brachionus, 260, Bristletail, scales of, 85. Bug, mouth of, 166, Bugula, 71. Butterfly, scales of, 90, 91. sucker of, 177. Chameleon-fly, 115. Cheese-mite, 253. Chilomonas, 457. Chirodota, 343. Cicada, drum of, 102. ovipositor of, 157, Cilia of Cydippe, 357. Infusoria, 452, 459. Rotifera, 257, 290. Cinclides, 411. Cnide, 379. Cockchafer, antenne of, 187. spiracle of, 114. Coleps, 456. Contasels Bladder, 435, 453. Corkscrew Coralline, 71. Corynactis, weapons of, 423. Cothurnia, 467. Cows’ paps, 400. Crabs, 197. ears of. 197. eyes of, 201. stages of, 210. Cranefiy, spiracle of, 113. Craspeda, 418. Cricket, ‘drum of, 97. Cuckoo-fly, ovipositor of, 145. Cuttleshell, 44. Cy athina, weapons of, 417. Cyclops, 203. Cydippe, 356. Cypris, 208. Daphnia, 207. Dead men’s fingers, 400. Diamond beetle, scales of, 92. Dragon-fly, 80. eye of, ‘193. Dumb-bells of Holothuria, 342 Dyticus, foot of, 134. Earthworm, 298. Ecthorzum, 421. Egger-moth, 188, Euglena, 444, Eunice, 308. Euplotes, 475. Eyes of Crabs, 201. Dragon-fly, 193. Harvestman, 241, Infusoria, 444, Insects, 193. Rotifera, 272, 446. Scallop, 60. Snail, 61. Spider, 238. Feathers, structure of, 16. Fission of Infusoria, 450, 462. Flea, mouth of, 170. Fly, antenna of, 192, ‘flight of, 78. ee en ee ee See eee eee a _ Fly, foot of, 124. spiracle of, 112. tongue of, 175. wing of, 80. Foot of Actinurus, 287. Bee, 186. Beetle, 134. . Brach‘on, 262. Dinocharis, 280. Fly, 132. Silkworm, 140. Spider, 241. Wohiptail, 275, Foraminifera, 488. Frog, blood of, 33. F)oghopper, ovipositor of, 156. Galathea, 216. Gall-fly, egg-tube of, 146. Gnat, antenne of, 192. grub of, 118. Gnat, mouth of, 171. wing of, 84. Grantia, 441, 443. Grasshopper, sounds of, 99. Hair of Bat, 11. Bee, 14. Beetle, 15. Cat, 9. Hog, 6. Horse, 7. Man, 3. Mole, 9. Moth, 15. Mousegll. Sable, 10. Sheep, 8. Halichondria, 441, Harvestman, 241. Heart-urchin, 336. Horse-fly, mouth of, 168. House-fly, 78. Humble bee, 79. Hydractinia, 334. Infusoria, 444, Insects, 78. air-tubes of, 108. antenne of, 184, eyes of, 193. feet of, 124. mouths of, 160. sounds of, 97. stings, &c., of, 142. Jelly-fish, 355. Katedid, 98. Laomedea, 37a. medusoids of, 380, Lares, 396. Larva of Urchin, 347. Leech, 309. Limpet, tongue of, 52. Locomotion, variety in, 298 Lombrinercis, 308. INDEX. 47 =) Luminosity of Medusa, 367. Lynceus, 205. Madrepore, weapons of, 417. Medusa, 354. transformations of, 372. Medusoids of Laomedea, 380, Stauridia, 894, Megalopa, 210. Mite, cheese, 253. water, 255. Mollusca, ears of, 62. eyes of, 58. shells of, 43. tentacles of, 57, tongues of, 52. Moths, antenne of, 188. scales of, 89, 90. Mouth of bee, 163. Beetle, 160. Brachion, 266. Bug, 166. Flea, 169. Gnat, 171. House-fly, 167. Sea-worm, 307. Sword-bearer, 284. Tube-wheel, 291. Whiptail, 276. Murder, discovery of, 27. Nacre, 48. Nais, 301. Nucleus of Infusoria, 463. Nymphon, 251. Otolithes of Meduse, 368, Slug, 62. Ovipositor of cuckoo-fly, 146 Gall-fly, 146. Saw-fly, 148. Paramecium, 452. Pearls, 50. Pedicellarizw, 324. structure of, 325. use of, 330. Periwinkle, eating of, 55. tongue of, 52. Perophora, circulation in, 36. respiration in, 40. Phyllodoce, 306, Pleasures of Sea-shore, 374. Pudora, scales of, 87. Polymorphina, 438, Polynoe, 302 Polypes of Aleyonium, 403, Hydractinia, 389. Laomedea, 385. Lar, 396. Polystomella, 438. Polyzoa, 67. Proteus, 433. Protozoa, 480. Pseudopodia, 439, Robber, story of, 1. 480 Rotifera, 257. Sabella, 394. Sagartia, 421, Sarsia, 360. Saw-fly, ovipositor of, 151. Scales of Butterflies, 91. Bristle-tail, 86. Diamond-beetle, 93. Flounder, 23. Gnat, 84. Goldfish, 20. Perch, 19. Pike, 24. Podura, 87. Sugar-louse, 86. Wrasse, 23. Scallop, eyes of, 57. Sea-anemones, weapons of, 407. Sea-cucumber, 340. dumb-bells of, 341. Sea-mat, 70. Sea-mouse, bristles of, 303. Sea-shore, pleasures of, 374. Sea-urchin, spines of, 318, larvae of, 347. pedicellariz of, 324. pores of, 338. skeleton of, 319, suckers of, 332. ferpula, 313. Shell of Cuttle, 44, Haliotis, 49. Pearl-oyster, 47 Pinna, 47. Shore-crab, 210. Silkworm, foot of, 140. spinner of, 181. Skeleton Wheel-bearer, 278, Slug, ears of, 64. tongue of, 52, Snail, eye of, 61. Spicula of Aleyonium, 404. Chirodota, 343. Fish-scales, 25. Tlolothuria, 840, Sponges, 441. Synapta, 343. Spiders, eyes of, 288. fangs of, 236. foot of, 250. habits of, 234, silk of, 242. spinner of, 244. Spines of Heart-urchin, 336, Sea-urchin, 318. Spinner of Silkworm, 180, Spider, 244, Spiracles of Insects, 112, 114. Sponges, spicula of, 441. Stauridia, 391. Sting of Bee, 142. INDEX. Stylonychfa, 478. Suckers of Sea-cucumher. 340. Sea-urchin, 332. Sugar-louse, 86. Swan-neck, 449. Sword-bearer, 282. Synapta, 345. Tentacle of Cydippe, 356. Hydractinia, 388, Laomedea, 885. Scallop, 57. Thaumantias, 368. Thaumantias, 367. Thread-cells, 417. Tongue of Butterfly, 177. Fly, 175. Limpet, 52. Tongue of Periwinkle, 52. Slug, 52. Trochus, 53. Trachelocerea, 449. Transformations of Barnacle, 229. Crab, 215. Galathea, 216, Medusa, 372. Polype, 381. Sea-urchin, 345, 'Tube-wheel, 296, Vorticella, 467. Tripod Wheel-bearer, 286, Trochus, tongue of, 55. Tube-wheel, 291, Turris, 370. Urchin, Sea, 818. Vacuoles, 436. Vaginicola, 469 Vorticella, 466. Water-fleas, 207, 208. Weapons of Anemones, 40%. orynactis, 423, Madrepore, 418. Sea-worms, 302. Weevil, 185. scales of, 92. Wheel-bearers, 257. Wheels of Brachionus, 26 Chirodota, 343. Whiptail, 247. Wing of Bee, 82. Fly, 80. Gnat, 83. Wool, 14. Worms, 297. Zoea of Crab, 209. Zoophytes, 376. THE END. » , a Sy - As Se " ~~ ie : Ve Fo. 2 aly : « - ‘ ’ ‘ ‘ v4 * . LT . ’ . ‘ : f ° 7 ‘ s dé 7 7 A yy a : i , : , ’ . y 7 ? ¢ : é ' - i \ . ; M t ‘ ‘ e \ ; os ’ ‘ , ¢ . Z a - s : ‘ QL Gosse, Philip Henry 50 Evenings at the microscope PLEASE DO NOT REMOVE CARDS OR SLIPS FROM THIS POCKET UNIVERSITY OF TORONTO LIBRARY