Every naturalist should possess a microscope: in fact it is becoming every day more obvious that a man cannot be a naturalist without one. At any rate, those naturalists who wish for a notice in our pages must use the microscope or we shall be compelled to pass them over. Mr. Gosse had a true eye to the all-embracing nature of the study of natural history, when, in reply to the question of where he should go for the benefit of his health, “Now where shall it be? Leamington—Tonbridge Wells—Clifton? No, none of these; since I must go, it shall be to the sea-shore; I shall take my microscope with me; and get among the shells and nudibranchs, the sea-anemones, and the corallines.” And we will stake our medical reputation upon the success of such occupation in such districts in hundreds of cases like Mr. Gosse’s, where blue pill, hydrocyanic acid, and the most approved dietetical regimen have utterly failed. What can be more healthful than the exercise of body and mind in the fresh air of the sea-side, whilst seeking for the animal and vegetable treasures on the shore or in the waters of the ocean ?
But let us follow Mr. Gosse to the sea-shore. He went to Devonshire, and was not long before his microscope was unpacked; and, as it is impossible for us to describe all that he has recorded of what he saw under the microscope, we must content ourselves with giving a few extracts, as indicative of the pleasant things to be met with in his very pleasant volume. He has caught a pecten, and of course kept it alive for some days in a marine aquavivarium, by which term is to be understood a hand-basin of sea-water; but his pecten, as pectens and other sea creatures will do, dies:—
“The death of my little pecten gave me the opportunity of submitting some of the gemmeous specks to the microscope. With a power of 220 diameters, I distinctly perceived a large lens, a glassy coat investing this, which itself was buried for more than half its volume in an investiture apparently granular, of a yellowish brown colour, having an ill-defined circle near its anterior side, of a blackish hue. Under pressure with the compressorium, the lens was manifestly circular; the coloured socket discharged dark granules, and from the darkest part a deep crimson pigment, which did not appear to be granular.
“I submitted portions of the gills also to the same magnifying power. Each of the four laminæ consists of a vast number of straight slender transparent filaments, evidently tubular, and about l-15OOth of an inch in diameter, arranged side by side; or rather of one filament, excessively long, reverted upon itself again and again, at both the free and the attached end of the laminæ, throughout its whole extent. This repeated filament is armed on each of two opposite sides with a line of vibrating cilia, the two lines moving in contrary directions; by the action of which a current of water is made continually to flow up and down each of these delicate filaments: so that the blood which circulates in their interior (for they are doubtless blood-vessels) is continually exposed throughout this its long and tortuous course to the action of oxygen.
“Like all organic functions, the action of these cilia is not under the will of the animal. It is said that if, during life, a small portion of the gills be cut off, the motion of the cilia will convey the fragment swiftly away, with a smooth easy motion, through the surrounding fluid, in a definite direction. It does not cease even with the life of the animal. The specimen which I examined had been dead at least fifteen hours, yet when I placed the torn fragments of the branchia?, one after another, beneath the microscope, the energy of the ciliary action, as the wave flowed with uniform regularity up one side and down the other of every filament, filled me with astonishment. Even the next morning, twenty-six hours after death, when the tissues of the filaments were partially dissolved, the ciliary motion was still going on, on portions that preserved their integrity.”—p. 52-54.
The capture of a madrepore affords our naturalist an opportunity of examining its structure under the microscope. Nothing is more marvellous to the observer of the tissues of these animals for the first time than the filiferous capsules or thread-cells with which many of these creatures abound. In the madrepore certain salmon-coloured bands are observed, sometimes regarded as ovaries:—
“Having detached a minute portion of one of the bands, I submitted it to an uniformly graduated pressure on the Stage of the microscope, when I found that in its substance were imbedded a great number of filiferous capsules, exactly resembling, in essential points, those of certain Medusas.
“The capsules are transparent and colourless, in shape a long oval from l-65Oth to l-800th inch in length, and are seen to contain a thread closely coiled. When the pressure reaches a certain point, the capsule shoots forth from one end the elastic thread, which in a moment starts out like a spring to a length thirty times as great as that of the capsule: sometimes in a straight line, sometimes in a serpentine, or (as I rather believe) a spiral form. The capsules do not burst, yet, at the instant of the propulsion of their filament, there is a distinct crack heard.
“I now cut off carefully, with fine-pointed scissors, two or three tentacles from one fully expanded, and submitted them to the same scrutiny. The rounded head of the tentacle appeared rather rough or hairy at first, but, as pressure began to flatten it, filiferous capsules were seen to be protruding from the outline, which increased in number as the pressure proceeded, until an amazing multitude appeared, and the whole substance of the tentacle-head was seen to he literally composed of these capsules, as thick as spiculæ in any sponge, with only a slight quantity of gelatinous matter to hold them together. To see these thousands of little vesicles discharging their missiles in rapid succession, like the flights of arrows in ancient battles, was an astonishing sight. When the propulsion could be distinctly followed by the eye, there was always seen a little zigzag line on each side of the thread, reaching to a considerable distance from the base, which I at first thought indicated a delicate membrane pushed out from the orifice of the capsule by the projected thread, until it at length burst, and shrank back in folds around the base. The form of the capsules differed from that of those described above, in that they were proportionally longer and more slender, being in fact almost linear. I could not discover any capsules in the body of the tentacle, but only in the head.
“If, indeed, these projected bristles are so many darts injected into the bodies of those minute animals which are the prey of the Madrepore, accompanied, as we must suppose each puncture to be, to insure its effect, with a fatal poison,—does not their presence in the convoluted bands of the interior militate against the supposition that these bands are ovaries, especially as I have seen the curious manner in which these are appressed to the swallowed morsel? Is it unreasonable to conjecture that their office may be accessory to that of the tentacles, destroying what may remain of life in the victim, after it has been enclosed by the lips, and is consequently out of the reach of the tentacles ?
“This inference was confirmed by the results of further investigation; for, examining in the same manner other minute portions of the frilled bands, as I could detach them with the point of a pin, I at length found a piece in which the capsules were much more numerous, and vastly larger than any that I had yet seen, whether in the bands or the tentacleheads. They were fully l-3OOth inch in length, long-oval, but somewhat curved. Their size enabled me, with a power of 300 diameters, to see their structure much more distinctly.
“At the larger end is situated a lozenge-shaped body reaching to the middle: from the inner end of this, partly coiled round it, but extending through the remainder of the capsule, is the thread, lying in an irregular, rather loose spiral, the appearance of which differs considerably in different capsules. When it is projected, the whole contents of the capsule disappear from the interior, in a manner which induces me to believe, strange as it seems, that the lozenge-shaped body at least, if not the whole thread, is turned completely inside-out; for the extended thread is attached, not to the smaller, but to the larger end, without the least appearance of rupture.
“Now for the structure of the thread, or wire, for it is as elastic as steel. This is marvellously elaborate, especially when we consider its excessive tenuity, the threads of the largest capsules being less than l-7000th of an inch in diameter, and those of the smallest perhaps l-20000th of an inch. The basal part of the thread, to a length about half as great again as that of the capsule, is clothed with alternate series of triangular plates, laid one over the other, or imbricated, like the scales of an artichoke. About half of this portion is furnished with an armature of hairs rather closely set, standing out at right angles, like a bottle-brush; they are twice or thrice as long as the diameter of the thread, in the middle of the brush, but diminish to each end; the individual hairs taper to a point.
“I have offered a conjecture that the projection of the thread is an evolution of its interior, and I believe that it is a complete one through its whole length. I have, even since I wrote that conjecture, seen an example of the process, which I can scarcely describe intelligibly by words, but the witnessing of which left on my own mind scarcely a doubt of the fact. It was effected not with the flash-like rapidity common to the propulsion, but sufficiently slowly to be watched, and by fits or jerks, as if hindered by the tip of the lengthening thread being in contact with the glass. In consequence, probably, of this impediment, it took a serpentine, not a straight form, and. each bend of the course was made and stereotyped (so to speak) in succession, while the tip went on lengthening; and the appearance of this lengthening tip was exactly like that of a glove-finger turning itself inside out.
“The brush of hairs, I think, is originally enclosed in the lozenge at the large end of the capsule. Both the lozenge and the brush are wanting in the small filiferous capsules; when I observed them in the large ones, the suggestion occurred that I might have overlooked them in the smaller, on which I examined some afresh with the utmost care, but in each case, the thread, which at first occupied the whole cavity of the capsule without any lozenge, was simple when evolved.
“The capsules appear confined to the thickened edge of the frilled band, in which they are set side by side, pointing outwards.”—122-126.
We had marked many other passages, but the length of our last extract precludes further quotation at present. We may draw on Mr. Gosse’s pages at a future opportunity. Now all we have left ourselves to do, is to commend Mr. Gosse’s volume to the attention of our readers. It is not alone those who are about to visit the Devonshire coast that will find it* of interest, but all who are fond of nature and natural scenery as they present themselves by the sea-shore. The volume is illustrated by twenty-eight plates, most of which are coloured, affording lively illustrations of the objects observed. Many of these contain representations of the microscopic structure of the higher animals, and not a few are devoted to microscopic objects alone.
