The little Whiptail is as lively in its motions as it is elegant in its form. When swimming, it glides with considerable swiftness through the water, turning frequently on its course, and often partially revolving on its long axis. When inclosed, as is often the case, by two fragments of the filamentous Chara, it travels along the sides of its inclosure, nibbling, as it goes, the Hocculent and sedimentary deposits on the surfaces of the leaves. The long spine-foot is commonly carried inertly after it ; when the animal suddenly turns, of course the tail is bent at the basal joint, but it is not habitually whisked about, as is the tail of firachionus, nor is it so much used as a support or turning }X)int. The animal has the power of so using it, however, and of adhering with considerable force to the glass of the box, or the side of a phial by its point.

We have hitherto looked at our Botifera by transmitted light ; and their crystalline transparency renders them beautiful objects when thus exhibited. But we will now look at the Whiptail by the direct light of the sun upon it, condensed, but not to a burning point, by the bull's-eye lens.

It now possesses a peculiar beauty of another character. The body generally is colourless as a vase of glass, but reflects the rays brightly from its polished surface. An advancing egg in the ovary is opaque white, as is the front part of the mastax ; the stomach and the intestine rilled with vegetable matter are of a yellow green ; the rotating head appears of a pale blue, and the eye shines out as a speck of opaque vermilion.

With the dipping-tube I will now take up a drop of water from the bottom of the Chara-j&r, allowing a little of the loose sediment to flow in also. This is a random cast ; we know not what we may get, though we are pretty sure to catch something. Xow then for the examination. Ha ! here is the curious Skeleton Wheelbearer, Dinocharis podUum, ;—nay, several of them.

This genus is remarkable for possessing true joints in the foot ; not merely telescopic inversions of the skin, but R permanent joints with swollen condyles, or rounded heads, resembling those of the antennas of a beetle. Hence the Skeleton has great freedom and precision of motion ; using the tips of the long toes as a fixed point, it throws its body hither and thither to a great distance, with remarkable agility. These joints admit of forward and lateral flexure, but you never see the body brought backward beyond a perpendicular position, the swelling of the terminal portion of each articulation precluding further motion in that direction; just as the joints of our knees and elbows permit bending in one direction, but not in the other.

This is another indication that these divisions are true joints ; and I direct your attention to the point, because the fact helps to indicate that this class of animals has its proper affinities with the Articulata, which has been denied by most naturalists.

The form is curious. Elevated at the summit of a long foot, consisting of three joints, which surmount two unusually lengthened and slender toes, is a vase-shaped lorica, which is three-sided. Its surface is covered all over with minute points, very closely set, so that it resembles shagreen ; besides which it forms numerous sharp ridges, which run across transversely. The two sides run off into thin lateral wings, which come to a sharp edge ; the back angle also forms a ridge, but less sharp and thin. In front, the shell, or lorica, is as it were cut off abruptly, like the rim of a goblet ; but out of this rises a second column, connected with the rim by an elastic membrane, which allows some freedom of motion. This column is widely divided in front and behind, and rises to a point on each side. When the rotatory front is withdrawn, these points approach and meet, closing the orifice ; but when the head is protruded they are widely separated.

Internally, we see the usual viscera contained in so narrow a cavity that we are ready to suppose the walls of the lorica unusually thick ; this is, however, an optical illusion, dependent on its dilatation into those angular wings already noticed. The cavity penetrates into them ; for in one of these specimens I see those curious twisted threads that are believed to be connected with respiration, within the lateral wings. The stomachs are generally full of green and brown food, but they will not imbibe carmine.

SKELETON "WHEEL-EEAREB.

Let us look, however, a moment longer at the singular foot. Between the first and second joints there are two projecting spines ; these differ much in different individuals as to their length, slenderness, and direction ; somer 2

times being quite short, at others as long as the toes ;• generally, they arch downwards, but occasionally they stand out straight or even curve upwards. In some specimens the spines appear to be processes of the first joint, but in others we can see distinctly that they belong to a little intermediate piece between the first and second apparent joints. Between the two toes, on the hinder aspect, projects from the last joint a small spine, which is perhaps the rudiment of a third toe, since we find that number in some genera of this class. The whole foot, including the toes, is rough with the shagreen-like points that cover the lorica.

You have already noticed the rapidity and fitful irregularity which the long and many-jointed foot confers upon the movements of this curious little form. From the toe-tips, as a point of adhesion, it throws its body to and fro, or from side to side, in a peculiar manner. The toes are sometimes sprawled out, like the legs of an expanded pair of compasses ; and sometimes the joints of the foot are suddenly bent in zig-za"g fashion, and then as abruptly straightened. The animal swims gracefully, but only with moderate swiftness, the rotatory crown of cilia beinc small, though forming the usual vortices when the animal is moored : while thus swimming, the toes are gracefully stretched behind, nearly in contact with each other. It is lively in its motions, but these seem performed without any ostensible object : we do not often see it attempt to eat, or nibble at any substance.

I think we never find the Skeleton except among the sediment at the bottom of the water in which it is kept ;. among which also we frequently seethe remains of defunct specimens—the skeleton of the Skeleton ; this itself makes a pretty object : the lorica, with its point and ridges, the thoracic column, the foot with its joints and spines, and the toes, all being perfectly preserved, and rendered even more clear than during life, because of the removal of all the soft internal parts by decay, and by the efforts of those little scavengers, the smaller species of infusorial animalcules. These quickly find their way into the interior of any dead animal with a shelly case, as a Wheel-bearer, a Water-flea, or an Insect, and soon devour every particle of soft flesh, cleaning out the case in the most tidy manner.

Here is a tiny subject which will test your powers of observation, and possibly your patience, in satisfactorily defining its structure, partly on account of its swift motion and irregular leaps, and partly on account of its extreme transparency. It is a crystalline cup, somewhat like the body of a wine-glass, without any foot, but bearing many flat, sword-shaped processes, which, proceeding from the breast, commonly lie flat on each side, down the body, the points projecting below. These are evidently stiff and highly elastic, and their use is manifest to any one who sees the creature in active motion. It swims with a rapid gliding progress, head foremost ; but, at almost every moment, it makes a sudden forcible jerk or leap, backwards or to one side, and that so quickly that the eye often cannot follow it in the transition. The organs by which these jumps are effected are the long breast-spines, which are suddenly thrown out in various directions ; and they may frequently be seen extended the instant after a leap. When we consider that the creature is jerked often four or five times its own length, through so dense a fluid, we shall perceive how strong the muscular action must be which moves the lever-like spines. The creature is thrown irregularly, often with the side foremost, or the back ; or made to perform a somersault in the act. It is probably a sensitiveness to danger or annoyance that prompts these violent leaps ; at least, it frequently performs them after a momentary examination of any floating matter with which its course brings it into contact.

The rotatory organs, the source of the common gliding motion, are not very large or conspicuous ; the cilia appear to be set all along the brow. The eye is very visible ; it is placed near the front, and seems to be of a deep bluish-black hue.

I have not, however, as yet introduced the nimble little stranger by name. "We may call it familiarly the Sword-bearer, but Professor Ehrenberg has named it Polyarthra platyptera.

This eminent authority on all that concerns these minute forms has placed the species among those which are destitute of a horny lorica or shell. But he is certainly in error here ; for, as you may see, there is manifestly a stiff lorica, which covers the back and sides, but which gapes widely in the middle of the under side, throughout its length. From the lateral points, however, a membrane may be seen for a short distance, which doubtless protects the viscera from actual exposure.

The sword-like fins appear to be twelve in number, arranged in groups, or bundles, of three each; one bundle being set on each side of the dorsal, and one on each side of the ventral aspect, at about one-fifth of the entire length from the frontal points. These are all that we can ordinarily count ; but I have seen more ; one day, while examining a specimen that presented a vertical aspect to me—end-on, to speak familiarly—the fins being all expanded, I saw with perfect distinctness a seventh pair, proceeding from the middle of the breast. They are flat, thin, narrow blades, of exceeding delicacy ; all distinctly serrated on both edges, the teeth pointing from the base outward : each is strengthened by a central rib. They are jointed independently, on rounded shelly knobs, and are doubtless moved by strong muscles. Under pressure, the knobs and the fins are brought out with beautiful distinctness. Here again we have true jointed limbs.

On the front you may discern a pair of tiny antennae, each bearing a pencil of very fine bristles. And just below the level of their base, in the centre of the dorsal region, you see the large eye, of a deep red hue, so deep that it frequently looks as if it were actually and intensely black. Just below the eye, apparently, but considerably more towards the ventral aspect, there is a huge niastax, occupying almost half the length of the whole body. The jaws are very simple in their construction, and therefore very instructive, for they contain the same elements as in Brachionus; but from their excessive tenuity, and for other reasons connected with the form of the animal, they are calculated to tax to the utmost your perseverance and skill in manipulation to resolve them. They were an enigma to me for years.

The great mastax is pear-shaped, pointing obliquely towards the middle of the belly. This form is owing to the great length of the fulcrum, and the wide curvature

Page 38 of 66