shore upon submerged ledges of rock, feed upon whatever animal they can seize. We have seen that they sometimes turn upon their back and sides, as well as move horizontally, this enables them more readily to secure their food, with the aid of the numerous suckers in the vicinity of their mouth, which when once they are fixed, never let go their hold till the animal is brought within the action of their powerful jaws. Lamarck thinks they do not masticate, but only lacerate their food; but as two faces of cach of their pyramidal organs answer those of the two adjoining ones, and these faces are finely and transversely furrowed,' this looks like masticating surfaces. Bose, who appears to have seen them take their food, says it consists principally of young shell-fish, and small crustaceous animals; as the latter are very alert in their motions, it is difficult for the sea urchins to lay hold of them: but when once one of these animals suffers itself to be touched by one or two of the tentacles of its enemy, it is soon seized by a great number of others, and immediately carried towards the mouth, the apparatus of which developing itself, soon reduces it to a pulp.

Who can say that the All-wise Creator did not foresee all the situations into which this animal would be thrown, so as to provide it with every thing that its station and functions. require? Considering its internal organization and the nature of the animal itself, and that it holds a middle station between the polype and the Molluscans, in the former of which the development of muscle is very obscure, and in the latter very conspicuous, and that it cannot, like the former, fix itself by its base, and so support a polypary, or if endued with locomotive powers carry with it a heavy shell; these things considered, and the nature of its food, and the force necessary to prepare it for digestion, it was evidently requisite that it should be defended by a crust sufficient to afford a support, and give effect to its powerful oral apparatus, and yet light enough to vield to the efforts of its motive powers; but as this crust, from its composition and nature, was liable to be crushed by a very slight pressure, it required further means of defence, and with these its Almighty and Beneficent Creator has amply provided it, by covering it, like a hedge-hog, with innumerable spines, varying in length, and capable of various movements. The long ones, when erected, defend it on all sides, both from the attack of enemies and from the effects of accidental pressure, and we may conjecture that when the longer ones are couched to answer any particular purpose, the short ones may come into

1 PLATE III. Fre. 11.

play, and assist in keeping any pressure from the crust. Perhaps, as in the hedge-hog, the ordinary posture of the longer spines is couchant, and they are only erected when the animal is in motion or under alarm.

The wonderful apparatus which closes the mouth of the common or typical sea-urchin,' is another and striking proof that Creative Wisdom employs diversified means to attain a common end, the nutrition of the animal. The mouth of this animal is under its body, a situation far from favourable, according to appearance, for the mastication or bruising of its food: if its jaws move vertically, like ours or the mandibles of a bird; or if they moved horizontally, like those of insects, it would have been attended with no small trouble to an animal whose mouth was underneath, but its five pyramidal jaws with the points of the teeth in the centre, admit an action more accordant with the situation of the mouth. By means of its numerous muscles it can impart a variety of action to the mass and individual pieces that form its oral apparatus, so as to accommodate it to circumstances, a power not possessed by the higher animals. In those Echinidans, whose mouth is in the margin of the anterior part of the shell, no such powerful apparatus is observable, its situation being in front of the animal, it is not as it were under restraint, it has less occasion for the aid either of tentacles in its vicinity, or of a powerful apparatus of masticating organs.

By furnishing these animals with a set of peculiar organs to act the part of hands as well as feet, we have another instance of the care of Divine Providence to adapt every creature to the situation and circumstances in which it is placed. The legs and arms of the higher animals would be rather an incumbrance to an Echinidan, as well as a deformity; it is therefore furnished with a set of organs better adapted to its peculiar station, wants and functions, in a numerous set of retractile tubes capable of the necessary extension, fitted at their extremity with a cup acting as a cupping-glass or sucker, and enabling the animal to adhere, with irresistible force, to any substance to which it applies them, and discharging at the same time the functions of hands to lay hold of their prey and convey it to their mouth, of legs and feet to stay themselves upon, and of lungs to assist in their respiration.

The workmanship also in these animal structures is as beautiful and striking as the contrivance manifested in them is

1 Echinus edulis.

3 PTATE III. Fig. 5.

2 Ananchites, Spatangus, &c.

wonderful. Their protuberances, especially in the mammillary sea-urchin, their variously sculptured spines, their tentacular suckers, all by their perfect finish and admirable forms declare -The hand that made us is divine-since they exceed in all these respects the most elaborate human works.

The third and last section of the Echinoderms, or spinyskinned Radiaries, are the Fistulidans. Amongst these we may notice the Sea-anemonies, marine animals, fixing themselves to the rocks, but having the power of locomotion, which from a common base send forth what appear to be a number of stalks terminating each in what seems a many-petaled flower of various hues, so that those who have an opportunity of observing them from a diving bell, may see the sub-merged rocks covered with beautiful blossoms of various colours, and vieing with the parterres of the gayest gardens. Ellis, who was the first Englishman who opened his eyes to the beauties. and singularities that adorn the garden which God has planted in the bosom of the ocean, has named many of these from flowers they seem to represent, as the daisy, the cereus, the pink, the aster, the sunflower, &c.

These animals, at first, appear to come very near the polypes, especially the fresh-water ones,3 bearing a number of individuals, springing, as it were, from the same root, each sending forth from its mouth a number of tentacles, which are stated to terminate in a sucker, and by which also, like the other Echinoderms, they respire and reject the water; they also reproduce their tentacles when cut off. Portions of the base when divided are reproductive, but they do not separate from the parent till their tentacles are completely formed. Their internal organization, however, is much more advanced than that of the polypes. They have a separate alimentary sac or tube, surrounded by longitudinal muscles, and even nervous nodules or ganglions, and also several ovaries.

In mild calm weather, when the sun shines, they may be seen in places, where the water is not very deep, expanding their many-coloured flowers at the surface of the waters-but upon the slightest indication of danger, the flowers suddenly disappear, the animal contracts itself and wears the aspect of a mass of flesh. They as it were, vomit up their young, or the germs formed in the ovaries: but they sometimes force their way out from other parts. When inclined to change their station they glide upon their base, or completely detaching themselves, commit themselves to the guidance of the waves.

1 Fistulides, Lam.

2 Actinia.

3 Hydra.

Reaumur observed them use their tentacles like the Cephalopods, for locomotion. They fix themselves with so much force, that they cannot be detached without crushing them.

It is not wonderful that so many of the lower aquatic animals should have been mistaken for plants, when they so exactly represent their forms, their roots, their branches and twigs, their leaves and their flowers-but besides the irrita bility of the animal substance, which however is partially exhibited by some plants; there is another character which seems, as a strong line of demarcation, to be drawn between them, and to which I have before adverted; animals take their food by a mouth at one extremity of the body, plants by roots diverging from the other. The reproductive organs in the latter occupy the place and ornature of the nutritive ones in the former. The gay and varied colours of the blossoms, the infinite diversity of their forms, the delicious scent so many of them exhale, all are calculated to draw the attention and excite the admiration of the beholder, while the organs of nutrition are usually hid in the earth. Not so in the animal kingdom; the nutritive organs, or rather those that prepare the nutriment, are placed in the most eminent and conspicuous part of the body, in the vicinity of all the noblest avenues of the senses, while those of reproduction are placed in the most ignoble station, and are usually found closely united with those passages by which the excretions of the body pass off. In the Tunicaries indeed the mouth and the anal passage are usually very near to each other, and in the polypes the same mouth that receives the food rejects the feces, and it even sometimes appears to happen that an animal has been swallowed, and after performing the ordinary revolution in the stomach, has been ejected again in a living state.

1 See above, p. 74.

2 PLATE IV. Fig. 1.

CHAPTER VII.

Functions and Instincts. Tunicaries.

THE animals we have hitherto been considering were all regarded by Cuvier as belonging to his first class, the Zoophytes, and are continued therein by Carus; the latter, however, allows that the Echinoderms are somewhat removed from the class by the commencement of a nervous system. Lamarck's next class, the Tunicaries, which we are now to enter upon, form part of the headless Molluscans of Cuvier, and belong to that section of them that have no shells. My learned friend, Savigny, in his elaborate and admirable work on The Invertebrate Animals, who also considers them as a separate class, denominates them Ascidians, dividing them into two Orders, Telhydans and Thalidans. Many alcyons of Linné and others, are now referred to the Class we are treating of. The characters of the class may be thus stated: ANIMAL, either gelatinous or leathery, covered by a double tunic, or envelope. The external one, analogous to the shell of Mollus cans, distinctly organized, provided with two apertures, the one oral, for respiration and nutrition, the other anal; the interior envelope, analogous to their mantle, provided also with two apertures adhering to those of the outer one. Body ob. long, irregular, divided interiorly into many cavities, without a head; gills occupying, entirely or in part, the surface of a cavity within the mantle; mouth placed towards the bottom of the respiratory cavity between the gills; alimentary tube, open at both ends; a ganglion, sending nerves to the mouth and

anus.

These animals are either simple or aggregate; fixed or floating: the simple ones are sometimes sessile, and sometimes sit upon a footstalk. The aggregate ones possess many characters in common with the polypes, inhabiting, as it were, a common body, somewhat analogous to the polypary, except that it

1 Tunicata. 3 Ascidiæ. 5 Cynthia.

2 Mollusca Acephala. 4 Tethydes, Thalides. 6 Clavelina.