arrived at from the researches of the eminent German zoologist, to whom we are indebted for almost all we know on the matter.

Let me first premise that this beautiful helmet-shaped creature is not the future Urchin; and, strange to say, that only a very small portion of the present structure,, namely, the stomach and gullet, will enter into its composition. The helmet is a kind of temporary nurse, within which the future Urchin is to be formed, and by which it is to be carried from place to place by its ciliary action, while the young animal is gradually acquiring the power of independent life ; when the whole constitution of the nurse will waste away and vanish !

The first trace of the young Urchin is a filmy circular plate, which is not symmetrical with the helmet, nor formed even on the same plane, but appears obliquely fixed on the interior of the stomach, on one side, close to the arch of transparent flesh which stretches from one of the points of the vizor to one of the ear-points. Herr Miiller compares the larva (which is not helmet-shaped in every species) to a clock-case, of which the vizor, with its hanging gullet and mouth, forms the pendulum; and then the newly-formed disk represents the face of the clock ; only that it is put on the side instead of the front. Now this tiny disk gradually grows into the form and assumes all the organs of the Urchin, while the enveloping nurse, flesh, rods, and all, wastes away to nothing.

The disk, soon after its appearance, is seen to bear prominences on its surface, in which is traced the figure of a cinque-foil, the elements being five warts set symmetrically. These lengthen and grow into suckers, essentially identical with those of the adult, but most disproportionately large. In the five triangular interspaces between these, little points and needles of solid calcareous glass begin to form, very much like the crystals that shoot across a drying drop of a solution of some salt; these catch and unite, first into "|~-, and then into (-{-forms, and then into irregular networks. Meanwhile, fleshy cylindrical columns spring up from the surface, one in each of these interspaces, and presently develop within their substance a similar framework of porous glass; these soon are seen to be the spines, and each is seated on a little nucleus of network, on which it possesses the power of rotating.

At the same time pedicellariae begin to be formed; and, what is specially marvellous, they are first seen, not on the disk, which alone is to be the future Urchin, but on the interior wall of the helmet, which is even now in process of being dissipated, and even on the opposite side to that which carries the disk. They commonly appear four in number, arranged in two pairs ; and we can see in them —they being, like the suckers, large out of all proportion to the disk—the stem, and the three-leaved heads, which already exercise their characteristic snapping movements.

The disk is meanwhile enlarging its area ; and the spines and suckers, gradually lengthening, at length push themselves through the walls of the helmet; the hanging points and crest of which are fast diminishing by a kind of insensible absorption ; the ciliary movements become less vigorous,and the mouth closes up. But, correspondently, the Urchin isbeginning to acquire its own independent power of locomotion; for the suckers, now ever sprawling about, are capable of adhering to any YOU>*G SEA-VRCHIN: which DEVELOPMENT OF DISK. foreign body with they come into contact, and of dragging the whole structure about, by their proper contractions. The cilia that cover the thickened fringing band still exercise their powers, and are the last to disappear. x

When the disk has grown to such an extent as to spread over about half of the larval stomach, very little remains of the helmet, except the middle portions of the glassy rods and the ciliary bands; all the rest of this exquisitely modelled framework having vanished by insensible degrees, no one knows how or where. The stomach and gullet, indeed, are gradually sucked into the ever-growing disk ! But all the rest, flesh and rods, fringes, bands, and cilia, waste away to nothing.

The mouth of the larva has no connexion with the mouth of the Urchin. The little isolated patches of glassy network continue to spread through the flesh of the disk, until the whole forms one uniform structure, and constitutes a series of plates. The mouth is that spot in the centre, over which the calcareous frame is last extended ; and it is first distinguishable by the appearance of five glassy points, which soon develop themselves into the five converging jaws, which we see forming such a curious apparatus on the inferior side of the Sea-Urchin.

Actual observation has not traced the infant animal beyond this stage of the development ; but Professor Miiller has taken specimens, swimming in the sea, in which scarcely a rudiment of the larva remained. They had the form of round flattened disks, which freely moved their spines, and crawled about the sides of the vessel in which they were kept by means of their suckers, exactly in the manner of the adult Urchin.

"Thus ends this strange, eventful history;" and in reviewing it, one can scarcely avoid being impressed with a sense of the majesty of God in these His humbler works. By what wonderful, what unexpected roads does He arrive at the completion of His designs ! And if such things as these are only now bursting upon our knowledge, after thousands of years of man's familiar contact with the inferior creatures, how many more wonders may yet remain to be unfolded, as science pursues her investigations into the Divine handiwork !

Chapter XVII. Jelly-fishes

As this afternoon was delightfully calm and warm, the very model of an autumnal day, I took my muslin ringnet and walked down to the rocks at the margin of the quiet sea. Nor was I disappointed ; for the still water, scarcely disturbed by an undulation, and clear as crystal, was alive with those brilliant little globes of animated jelly, the Ciliograde and Naked-eyed Medusae, apparently little more substantial than the clear water itself. Multitudes of them were floating on the surface, and others were discerned by the practised eye, at various depths, shooting hither and thither, now ascending, now descending, now hanging lightly on their oars, and now, as if to make up for sloth, darting along obliquely with quicklyrepeated vigorous strokes, or rolling and revolving along, in the very wantonness of humble happiness.

After gazing awhile with admiration at the undisturbed jollity of the hosts, I made a dip with my net, the interior of which, on lifting it from the water, was lined with sparkling balls of translucent jelly. They were far too numerous to allow me to transfer them all to captivity ; they would soon have choked up and destroyed one another ; I therefore selected the finest and most interesting, shaking an example or two of each kind into my glass jar of sea-water, where they immediately began to frolic and revel as if still in the enjoyment of unrestricted liberty. And here they are.

Among these bright and agile beings which are shooting x 2 their wayward traverses across each other, and intertwining their long thread-like tentacles, we will select one or two for examination, as samples of their kindred. And first let me separate this active little Beroe (Cydipjjepomiformis), which I dip out with a tea-spoon and transfer to this other glass jar, that we may watch its form and movements unaffected by the presence of its companions.

We see, then, a little ball, almost perfectly globular, except that a tiny wart marks one pole, of the size of a small marble, and apparently turned out of pure glass, or ice, or jelly—according to your fancy,—perfect transparency and colourlessness being its characteristics ; so much that it is not always easy to catch sight of the little creature, except when we allow the light to fall on the jar in a particular direction. From two opposite sides of the globe proceed two threads of great length and extreme tenuity, which display the most lively and varied movements.

These filaments shall occupy us for a few moments. We trace them to their origin, and find that they proceed each from the interior of a lengthened chamber, on each of two opposite sides of the animal. Suddenly, on the slightest touch of some foreign object, one of the threads is contracted to a point and concealed within its chamber, but is presently darted forth again. When the lovely globe chooses to remain still, the threads hang downward, gradually lengthening more and more, till their extremities lie along the bottom of the jar extended to a length of six inches from the chamber. Then we see that this delicate thread is not simple, but is furnished along one side, throughout its length, at regular distances, with a row of secondary filaments, which project at right angles from the main thread.

These secondary filaments constitute an important element in the charm which invests this brilliant little creature. They are about fifty in number on each thread, and some of them are half an inch long, when fully extended, but it is seldom that we see them thus straightened; for they are ever assuming the most elegant spiral coils, which open and close, extend and contract, with an ever changing vivacity. The animal has a very perfect control over each thread, as well as over each individual secondary filament. They are, either together or separately, frequently projected from their chambers to their full extent, by one impulse; sometimes the extension is arrested at any stage, and then proceeded with, or the thread is par tially or entirely retracted. Sometimes the secondary filaments are coiled up into minute balls, scarcely perceptible, or only so as to give to the thread the appearance of small beads remotely strung on a fine hair; then a few uncoil and spread divergently ; contract again, and again unfold; or many, or all, interchange these actions together, with beautiful regularity and uniformity, repeating the alternation for many times in rapid succession.

The beauty and diversity of the forms assumed by these elegant organs beguile us to watch them with unwearied interest, and we wonder what is their function. For, with all our watching, this is by no means clear. They are certainly not organs of motion. At times it seems as if they were cables intended to moor the animal, while it floats at a given depth; for we see them with their extremities spread upon the bottom, to which they appear to have a power of adhering, thus forming fixed points, from which the little globe rises and falls at pleasure, shortening or lengthening its delicate and novel cables, maintaining all the while its erect position.

When the Cydippe swims, however, which it does with great energy, the threads seem unemployed, streaming loosely behind, and evidently taking no part in the progression, though still adding beauty and grace to the tout ensemble. The organs by which the sprightly motions of the whole animal are effected are of quite another character, and shall now engage our attention.

. You have doubtless observed, while gazing on the animal, a peculiar glittering appearance along its sides, mingled in certain lights with brilliant rainbow-reflections. Now let us take an opportunity, when it approaches the side of the glass, to examine this appearance with a lens. The globe, you see, is marked by longitudinal bands, eight in number, set at equal distances, and ranging like meridians, except that they do not quite reach to either pole. These bands are the seats of the motile organs, which are highly curious, and in some sort peculiar.

Page 48 of 66