ANIMALIA RADIATA. 143 



ORDER I. ECHINODERMATA PEDICELLATA. 



.) 



Envelope pierced with a great number of little holes, across 

 which pass membranous tentacula, terminated by a small 

 disk, fulfilling the office of vent-hole ; such are the Echini 

 or Sea-urchins and Sea-stars. 



ORDER II. ECHINODERMATA APODA. 



Body clothed in a coriaceous skin, without armour or vesi- 

 culous feet. 



ENTOZOA.* 



Body, in general, elongated or depressed, articulated or not 

 articulated, and without limbs ; no branchiae nor tracheae, nor 

 any other organ of respiration; no traces of a true circulation; 

 some vestiges of nerves, but sufficiently obscure, as many 

 naturalists have even doubted their existence; almost all live 

 within other animals ; there are hardly any tissues or cavi- 

 ties in which some have not been discovered; they have 

 even been observed in muscles and the cerebral substance. 

 The manner of their introduction into the animal economy 

 has never been satisfactorily ascertained. Two orders. 



* Intestinal Worms. 



