SUB-KINGDOM II. RADIATA. 



CLASS L ZOOPHYTA. 

 (POLYPES.) 



THE animals of this Class have a well-defined 

 form, though a more or less changeable one; a 

 form of which the most obvious characteristic is, 

 that the various organs are arranged in a radiate 

 or circular manner round a centre. In the simplest 

 state one of these animals consists of a fleshy bag, 

 opening only at one end, around which is placed 

 a crown of slender contractile threads called tenta- 

 cles, while the other end forms an adhesive disk 

 by which the creature attaches itself to other 

 objects. This is the condition of the Hydra, the 

 Clava, &c. 



A number of species have the power of secreting 

 an investing tube of a horny nature, in which the 

 fleshy body can move up and down, expanding its 

 tentacles, like a star, over the top. Others give 

 forth buds at intervals, each of which takes the 

 form of a polype ; and these being permanent, give 

 a shrub-like or branched aspect to the animal, 

 which then is a compound polype. The tube is 

 branched conformably, and the orifices from which 

 the polypes expand are usually dilated into cups 



