394 RADIATA. 



oviparous ; and some seem to be reproduced bygemmce or buds, 

 or simply by a division of their parts. 



The conglomerated or compound arrangement of animals, of 

 which some examples occur among the Mollusca, is a common 

 circumstance among the Radiated Animals, particularly among 

 those named Polypi ; and from their aggregation and expan- 

 sion into trunks and branches of various forms, joined to the 

 simplicity of the organization in the greater number of the spe- 

 cies, originated the term Zoophyta, or animal plants. The 

 radiated disposition of their organs, like the petals which form 

 corolla of a flower, seems also to have led to this idea. Indeed 

 the boundary line between the animal and vegetable kingdom 

 seems at first view to be but indistinctly drawn ; and there are 

 objects in both which even accurate observers are scarcely 

 able to decide, whether they belong to the one or the other. 

 In the simplest being, however, the globular form, as Carus 

 observes, is the characteristic of animality ; and minute micro- 

 scopical investigation detects in the lowest of the animal races a 

 semifluid mass, composed of minute globules suspended in slimy 

 fluids, while in the vegetative organization the cellular texture 

 always predominates. To this characteristic form the most imper- 

 fect animated beings add a sensibility to the faintest impressions, 

 that of light, for example, the power of voluntary motion either 

 in the animal or its parts, and the absorption of food into an in- 

 ternal cavity. In the more perfect animals the osseous skeleton 

 serves to cover and protect the central nervous masses, and to 

 support the organs of motion ; but in the simple structure of 

 the lower animals, the frame-work serves only the last of these 

 purposes, being either external to the animal substances, as in 

 the Tubiporce and Sponges, or internal, as in the Sertularice, 

 Gorgonice, &c. 



The animals of this division have been arranged in five clas- 

 ses, viz. 



I. ECHINODERMATA, or animals with a crustaceous covering, 

 distinct intestinal canal, and organs for generation, respiration, 

 and partial circulation. 



II. ENTOZOA, or intestinal worms ; elongated and depressed 

 animals which have no organs for respiration or circulation. 



III. ACALEPHA. Animals of a circular and radiated form, 

 and destitute of circulating and respiratory organs. 



