As this current passes, the manducatory apparatus acts upon the particles of food which it brings in its course. The quadrant-shaped masses approach each other and recede, with a rapid rolling movement, in the direction of the curvature of the mallei; while, at the same time, the rami of the incus open and close their points, rise and sink, and occasionally perform a kind of shovelling action. The points of the fingers of the unci, meeting each other, doubtless pierce and tear the Infusoria swallowed, and the striated faces bruise, squeeze, and grind them down.

AVhen the muscular investment is dissolved away by potash, the essential identity of the whole structure with that of the type already described becomes abundantly evident. Even the mallei, which in some aspects present difficulty, when viewed vertically, are but little changed ; the fingers are parallel instead of divergent, and the handle-like character of the manubrium is lost; but three areas, inclosed by loops or carina? of solid substance, reveal their true nature.

We will now see if we can separate the animal from its tube, so as to examine its lower parts. By a gentle pressure upon the bottom of the tube with the edge of a penknife, which I bring to bear upon it by the aid of this simple microscope, the creature is induced to wriggle out of his case. Replacing now the cover of the live-box, and placing it again on the stage of the compound microscope, we" see that the lower part of the body forms a foot analogous to that of a Brachionus, covered with ring-like wrinkles, and separated from the body by an abrupt constriction and diminution of the diameter. At the very extremity there is a sort of sucking-disk, by which we may presume the hold of the animal upon the plant is maintained. No organic connexion subsists between the foot and the tube; for the latter is not an essential part of the animal, though absurdly called a lorica by Ehrenberg, but only an accumulation of mucus successively exuded from the body, and thrown off in the form which it possesses by the contractions and other movements of the body.

But see ! the poor naked creature is writhing in contortions, which become more and more convulsive and spasmodic: and now it evinces great rigidity in these, till the body has become almost shapeless, portions of the surface being here and there violently forced out into projections, and the foot strongly curled up. The only signs of life that now remain are the occasional fitful workings of the jaws. Are we then to suppose that the shelter of the gelatinous case is needful to its continued existence % or did I inflict a mortal injury upon it when I laid the edge of my penknife upon its lower part to drive it forth % Most probably the latter is the true solution.

Out of the colony that remains, we will now select another specimen, with ripening eggs, in order to watch the development of the young. Here is one with three eggs lying obliquely in the tube, one of which is already showing the impatient movements of the embryo within.

! now the egg-shell has burst, and the little creature escapes from its prison, and quickly makes its way to the mouth of the parent-tube. Now it is free, and swims away rapidly, in a giddy, headlong manner. It is quite unlike its mother ; for its form is trumpet-shaped, resembling that of a Stentor with a wreath of cilia around the head, interrupted at two opposite points : the central portion of the head rises into a low cone. There is as yet no trace of the beautiful double-petalled flower.

It has been whirling giddily about the live-box for about a quarter of an hour, but now it begins to manifest tokens of weariness; or rather the time is approaching for it to select a place of permanent sedentary abode. Its motion is sensibly retarded : it now and then adheres to the glass momentarily, by its foot, and moves forward by successive jerks, not proceeding more than its own length at a time ; and this apparently with effort. The periods of its remaining stationary become longer, so that you may suppose it finally settled twice or thrice, before its wanderings are quite over, some shock or alarm sending it off to a little distance again.

At length it wanders no more; its foot holds fast to the glass, and its movements are confined to whirlings round and round on this as a pivot, and to sudden contractions of length. Presently we see a very delicate film surrounding the point of attachment;—the first rudiment of the tube, a ring of mucus thrown off from the skin, and pressed down to the foot by the contractions of the body. Meanwhile, the ciliary crown is dividing itself into two, and now we see already the essential form and appearance of the mature animal, every moment developing its perfection.

Chapter XV. Worms

An examination of the diverse modes in which locomotion is performed among animals, and the various organs and modifications of organs that subserve this important purpose, would form no uninteresting chapter in natural history. You have two feet ; your dog has four ; in the bird, two of these are converted into wings, with which it rises into the air; in the fish all of them are become fins, with which it strikes the water. But it is in the invertebrate classes that we discover the strongest variations. The Poulpe "flops" awkwardly but vigorously along, by the alternate contractions and expansions of the web that unites its arm; the Snail glides evenly over the herbage by means of its muscular disk; the Scallop leaps about by puffs of water driven from its appressed lips; the Lobster shoots several yards in a second by the blow of its tail upon the water ; the Gossamer Spider floats among the clouds upon a balloon that it has spun from its own body ; the Centipede winds slowly along upon a " hundred" pairs of feet ; the Beetle darts like an arrow upon three ; and the Butterfly sails on the atmosphere with those painted fans which are properly "aerial gills." How elegantly does the Planaria swim by the undulation of its thin body, and the Medusa by the pumping forth of the water held within its umbrella ! How wondrously does the Echinus glide along the side of the tank on its hundreds of sucking-disks ! How beautiful, and at the same time how effective, are the ciliary wheels of the Brachionus !

worms.

I am now going to show you some other examples of travelling machinery, in an humble and despised, but far from uninteresting, class of animals,—the Worms. Here is an Earth-worm upon the garden-border. With what rapidity it winds along, and now it pokes its sharp nose into the ground, and now it has disappeared ! If your eye could follow it, you would see that it makes its way through the compact earth not less easily nor less rapidly than it wound along the surface. If you take it into your hand, you perceive no feet, wings, fins, or limbs of any kind ; only this long cylinder of soft flesh, divided into numerous successive rings, and tapering to each extremity. The very snout which you saw enter so easily into the substance of the soil, is no hard bony point, but formed of the same soft yielding flesh as the other parts. And yet with no other implement does the lithe worm penetrate wdiithersoever it will through the ground. How does it effect this 1

The fineness of the point to which the muzzle can be drawn is the first essential. This can be so attenuated that the grains of adherent soil can be readily separated by it ; when its action becomes that of the wedge. The body being drawn into the crevice thus made, the particles are separated still farther. Now another provision comes in; the whole surface of the skin secretes and throws off a quantity of tenacious mucus or slime, as you will immediately perceive if you handle the Worm ; this has the double effect of causing the pressed particles of soil to adhere together, and then to form a cylindrical w r all, of which they are the bricks, and the slime the mortar; and also of greasing, as it were, the whole interior of the burrow or passage thus made, so that the Worm can travel to and fro in it without impediment ; while the fact that the slime is continually poured forth afresh prevents the least atom of earth from adhering to its body. This you have doubtless observed, or may observe « 9 in a moment, if you will take the trouble to thrust a spade into the ground, and give it two or three shakes. You will presently see on all sides the alarmed Earthworms coining swiftly to the surface, and will notice how perfectly sleek and clean they are.

But these contrivances are only accessories : we have not yet discovered the secret of the easy movement. The mere elongation of the snout is no explanation of the disappearance of the Worm in the burrow ; for you will naturally and reasonably say that this elongation cannot extend beyond a certain limit; and what then? Xo further progress can be made unless the hinder parts of the body are, by ;—but contraction, drawn up towards the elongated front what holds the front in place meanwhile 1 Why, when the muscles contract, does not the taper, wedge-like muzzle slip back, and lose the ground it had gained 1

This we will now look at. I take up this Worm, and put it into a narrow glass cell, where we may watch its movements. It presently begins to elongate and contract its body vigorously, apparently alarmed at its unwonted position ; and the mucus is thrown off in copious abundance. We apply a low microscopic power to it, and catch glimpses, now and again, as it writhes about, of a number of tiny points protruded and retracted, with great regularity, through the skin. Its mobility precludes our discerning much more than that these points are very numerous, that they are arranged in four longitudinal lines, running along the ventral side of the animal,—two lines on each side,—and that in each line there is a point protruded from each of the many rings of which the Worm's body is made up.

In order to see a little more of these organs we must sacrifice a Worm ; having killed it, and divided the body in the middle, I cut off, with sharp scissors, a small transverse portion, say two or three rings, and press the fragment between plates of glass. Now, with a higher magnifying power, we discern in the midst of the translucent flesh the points in question. They are not, however, single; but each protrusile organ consists of a pair of transparent, brittle, glassy rods, shaped like an italic J] of which the recurved points are directed backwards when thrust out from the skin.

The mode in which these assist the progression of the Worm is well described by Professor Rymer Jones. " The attenuated rings in the neighbourhood of the mouth are first insinuated between the particles of the earth, which, from their conical shape, they penetrate like a sharp wedge ; in this position they are firmly retained by the numerous recurved spines appended to the different segments ; the hinder parts of the body are then drawn forward by a longitudinal contraction of the whole animal ; a movement which not only prepares the creature for advancing further into the soil, but, by swelling out the anterior segments, forcibly dilates the passage into which the head had been already thrust : the spines upon the hinder rings then take a firm hold upon the sides of the hole thus formed ; and, preventing any retrograde movement, the head is again forced through the yielding mould ; so that, by a repetition of the process, the animal is able to advance with the greatest apparent ease through substances which it would at first seem utterly impossible for so helpless a being to penetrate." *

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