The whole field is now filled with scattered granules of irregular form and size, of a dark red hue. These are the particles of carmine floating in the water ; particles of alumina, that is to say, stained with cochineal. They are in motion, and their movement is more energetic the nearer they are to the little animal, which is rotating vigorously in the midst of them. They describe two great circles, concentrical with the twowheelsof the Brachionus, and it is easy to see that their rotations are the cause of the movement. The motion of the cilia communicates itself to the surrounding water, and produces circular currents, into which every floating atom within a certain distance is drawn, and in which it then continues to whirl round with a rapidity which increases as it approaches the centre of rotation.

But the Bracldonus suddenly lets go its foot-hold, and a surprising change takes place. Ko more currents are made in the water, but the animal itself glides swiftly away head foremost with an even course, revolving on its axis as it goes. What is the immediate cause of its movement 1 The ciliary action which before produced vertical currents.

In order to explain this, let me suggest to yon a homely comparison. Suppose you see a boat on a still lake, and in it a man pulling a pair of oars. He pulls vigorously, but the boat does not move an inch, and you perceive that she is fast moored ; a rope holds her to a post on the bank. But does the man's rowing produce no effect 1 O yes; the successive strokes of the oars upon the water have communicated motion to the fluid, and a strong current is made on each side of the boat, in a direction opposite to that in which he strives to row her forward, the force of which is felt to a distance proportionate to the vigour and continuance of his pulling. The reason of this is that the boat is fixed, and all the force of the impact is spent on the water.

But now another man approaches the post, and unties the rope. Instantly the boat glides ahead, and continues to do so, urged by the repeated strokes of the oars, whose effect on the water in making currents is now slight and imperceptible. The reason of this is that the water is now a fixed body (or nearly such), and the force of the impact is mainly spent on the movable boat.

The Brachionus is the boat, its cilia are the oars, and its foot is the rope. As long as this last maintains its hold, the whole force of the ciliary stroke is spent on the water, and currents are the result ; but as soon as this hold is broken, the force acts on the animal (= boat), which is thus rowed rapidly forwards.

The use of the cilia in this latter case is obvious. They enable the little animal -to rove about at its wayward will ; and doubtless motion is as pleasant and necessary to it as to the fish in the sea, or to the bird in the air. But what is the object of their vigorous rotation, when the animal chooses to maintain a firm hold with its foot % What is the use of rowing a boat, if you do not choose to let go the painter 1

To solve this enigma, let us search up our little Brachion once more; he will not roam long before he settles soberly again. Yes, here I have him moored. Now, mark carefully the vortices, or whirlpools, which are so vigorously circling round the animal's front, and you will perceive that the movement is not a strictly circular one, but that each whirlpool has an outlet close to the cilia; for the accumulated and condensed particles of pigment, after many rotations pass off in an united stream between the two crowns, and go away horizontally in a line from the ventral side of the front. That is to say, each vortex pours off its accumulation at a point on the inner side of the ciliary circle, and the two streams, uniting, pass off from the lip of the shell, to be drawn in again, however, by-and-by, when the centrifugal force is exhausted.

Now this stream passes immediately over the mouth, which is an opening in the flesh of the front, forming a deep cleft on the ventral side, the lips of which, as also the whole interior of the tube, of which it is the orifice, are richly covered with cilia. A certain portion of the atoms are thus arrested by these cilia, and are hurled by their vibrations clown this gulf. Yet not all, nor nearly all; for the lips appear to possess the sense of taste, or of some modification of touch, which enables them to refuse or to receive the atoms presented to them, so that only such particles pass down the throat as are selected for food. Some of the atoms of pigment are admitted, and one of the most pleasing sights connected with these animals, is to watch the swallowing of coloured food, its reception into the singular sunken mouth, where the great powerful jaws act upon it: thence its dismissal through the gullet, where certain glands pour upon it their secretions, into the stomach, where other glands, answering to a liver, change it ; and thence into the intestine and rectum, until its indigestible portion is discharged through the cloacal orifice.

The object of the mingling of colour Avith the water in which these and similar animals are held for observation, was the tracing of the phenomena of digestion. And, indeed, it renders the whole process beautifully distinct; for, from the transparency of the tissues, the presence of the coloured pellet is everywhere recognizable, since it retains its form and hue under all its changes, clearly revealing to us the shape, dimensions, and directions of the various canals through which it passes; here and there diffusing throughout the viscus in which it is held a beautiful roseate hue, more or less deep, without, however, causing- it to lose its own definite outline.

Let me now direct your attention to the organs devoted to the seizing and mastication of the food. And the more, because the form of these organs in the Rotifera is quite peculiar, quite unlike what is found in any other class of animals; though the parts are essentially the same as those which we have already seen entering into the mouth in insects.

Removing the carmine-stained water, I put into the live-box a drop from a vase very rich in organisms of many kinds. Among these you see very numerous the mulberry-like clusters of that beautiful green creature,, Syncrypta volvox, which is now pretty generallyconsidered a plant ; though from its spontaneous motion, swimming evenly along, revolving on its axis as it goes, you would be inclined to asjree with earlier observers in thinking it an animal. These appear to be favourite morsels with the Brachion : one has already been devoured, and is quite visible in the alimentary canal, its brilliant green hue shining out through the translucent viscera and tissues. Others are approaching, "-;, and two or three are iust 0> now drawn into the vortex of the ciliary current. It is amusinff to see the manoeuvres which the J3rachionus makes to take his prey. I say manoeuvres ',. for there reallv •J seem to be perception and intelligence. The mode inwhich it directs its ciliated flaps towards the spot where a Syncrypta is whirling, or suddenly stretches forward to the extent of the long foot, as if it would seize the prey by force, seems to indicate a cognizance of its proximity; as do also, still more, the manner in BKAC'HIOXUS. which it depresses the liplike lobes of the rotatory organ on one side, when the prey is in the vortex on that side, and the eager haste with which it shrinks down into its shell the instant the little mulberry drops at length into the throat.

But now comes the tug of war; the black, millstone-

like jaws open wide, and stretch forward to grasp the little victim (which is still distinctly visible through the transparent tissues) : they touch the globular envelope, but cannot quite grasp it. The Brachion redoubles its efforts ; the jaws gape vigorously, but can only scrape the sides of the little globe, which at every touch slips away, the expanse of the jaws being not quite sufficient to embrace it.

At last the little animal becomes indignant ; the jaws no more endeavour to grasp, but with a very distinct and sudden upward jerk throw out the prey, which until now has been retained and pressed downward by the contraction of the sides of the sensitive throat. Strange to see, the little Syncrypta, after all its imprisonment and rough handling, is no sooner free than it whirls merrily away,, revolving as it pursues its even ciliary course, just as if no interruption of its freedom had occurred.

Meanwhile, however, better success attends the Brachion's hunting ; for a smaller globe has sunk into the throat, and passed with a gulp into the mouth between the gapingjaws; which instantly close upon it, and,working vigorously, bruise it down with a hammer-like action upon a sort of central table. After this process has gone on for a few minutes, the green mass, less perfectly denned than before, slips through a narrow postern-gate, along a short slender alley, into the digesting stomach.

But what sort of a mouth is this 1 It is inclosed within the tissues of the body, not very far from its centre, so that no part of it comes into contact with the external water, or even approaches any portion of the superficies of the body. It has been usual to call the great hemispheric bulk in which the symmetrical hammers work so vigorously, a gizzard ; but it is a true mouth, and the hammers are true jaws.

This form of mouth is termed a mastax ; it consists of a dense but transparent muscular mass, forming three lobes at its lower part, deeply cleft at the front of its ventral side, where the passage, which I have called the throat, but which is more correctly designated the buccal funnel, enters. Within this muscular bulb are placed two bent organs like hammers, called mallei, and a third central table, called the incus. The mallei approach each other dorsally, while the incus is placed towards the ventral side, its stem pointing obliquely away from the centre.

Each malleus consists of two portions, united by a free but powerful hinge-joint. The lower joint (manubrium) is shaped somewhat like a shoulder-blade ; and the upper joint (uncus)* is set-on at nearly a right angle to it, but is capable of considerable change of direction by means of its hinge. It consists of five or six finger-like teeth, connected by a thin web of membrane.

The incus also consists of several distinct pieces. The principal are two stout rami, resting on what appears, when you look at the back or belly of the animal, to be a slender foot-stalk (fulcrum). But when you get a lateral view, the foot-stalk is seen to be only the edge of a thin plate, to the upper edge of which are jointed the rami, in such a manner that they can open and close, like the blades of a pair of shears. Each ramus is a thick, threesided piece, with the upper side hollow, and the inner flat, and in contact with that of its fellow, in a state of repose. The uncus of each malleus falls into the concavity of its corresponding ramus, and is fastened to it by a stout triangular muscle, which allows some freedom of motion.

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