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Show 32 INTUODUCTION. f1•om the circulation in closed vessels to nutrition by imbibition, and the corresponding one of respiration in circt~ms~ribed organs to that effected by trachere or air-vessels distributed throughout the body. In them, the organs of taste a~d sight are the most distinct; one single family alone presentmg that of hearing. Their jaws, when they have any, are always lateral. . The fourth form which embraces all those animals known by the name of zoo~hytes, may also properly be denominated .Jlnimalia Radiata, Or radiated animals. We have seen that the organs of sense and motion in a11 the preceding ones are symmetrically arranged on the two sides of an axis. There is a posterior and anterior dissimilar face. In this last division, they are disposed like rays round a centre; and this is the case even when they consist of but two series, for then the two faces are similar. They approximate to the homogeneity of plants, having no very distinct nervous system or particular organs of sense; in some of them, it is even difficult to discover a vestige of circulation; their respiratory organs are almost uni versally seated on the surface of the body, the intestine in the greater number is a mere sac without issue, and the lowest of the series are nothing but a sort of homogeneous pulp, endowed with motion and sensibility.(!) (1) Before my time, modern :naturalists divided all invertebrated animals into ~wo classes, Insects and Worms. J was the first who attacked this method ; and m a memoir read before the Society of Natural History of Paris on the lOth of ~ay ~795, and printed in the Decade Philosophique, I presented a new division, m wluch I marked the characters and limits of the Mollusca, Crustacea, Insects and Worms, Echinodermata and Zoophytes. In a memoir read before the Insti· tute on the 31st of December 1801, I ascertained the red-blooded worms or Anne· ~ides. And finally, in a memoir read before the Institute in July 18i2, and printed m .the Annale~ du Museum d'Histoire Naturelle, tome xix, I distributed these var1ous classes m three divisions, each of which is analogous to a branch of the vertebrata. |