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 submerged rocks covered with beautiful blossoms of various colours, and vying 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,1 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 germes 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. 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 irritability 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 ;'

See above, p. 139.

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 than an animal has been swallowed, and after performing the ordinary revolution in the stomach, has been ejected again in a living state.

1 PLATE IV. FIG. 1.

218

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,1 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, Tethydans and Thalidans. Many alcyons of Linné and others, are now referred to the Class we are treating of.

3

4

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 Molluscans, distinctly

1 Tunicata.
3 Ascidia.

2 Mollusca Acephala.
4 Tethydes, Thalides.

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 oblong, 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 is more intimately connected with the animal that inhabits it: the mouth of all is surrounded with rays or tentacles, as is also, in many, the anal orifice; but in their organization they differ very widely, exhibiting traces of a nervous system, and even, in some, of one of circulation. The fixed ones are commonly attached to rocks or other inorganized substances, but sometimes they are parasitic; thus a species of botrylle3 envelopes, like a cloak, certain asci

1 Cynthia.

2 Clavelina. 3 Botryllus polycyclus.