PRIMAEY DIVISIONS AND CLASSES. 



209 



also to this primary division that we must refer the tur- 

 bellaria, whose body is without limbs, and whose nervous 

 system is composed essentially of two lateral cords springing 

 from two cephalic ganglions. The intestinal worms, or 

 helminthise, belong also to this division; their structure is 

 very simple ; they present only vestiges of a nervous sys- 

 tem, and yet are intimately allied to the annelides, which 

 often seem to be in some measure the degraded representatives 

 of the same zoological type.* 



b a 



t e 



Fig. 157. Social Ascidise.f 



To place the classification of annulated animals in harmony 

 with the differences which we have pointed out in the nature 

 of these beings, they must be divided into eight distinct 



Fig. 158. Porcelaine (Cypraea). 



Fig.l59.-Cpqui]le 

 de Paludine, or 

 Shell of the Pa- 

 ludina (Helix). 



* Naturalists are not agreed in respect of the classification of the entozoa, 

 or intestinal worms. Cuvier arranged them amongst the radiata or zoophytes ; 

 but they more resemble the annelides in the conformation of their bodies. 



t Ascidiae of the genus Porophora ; 6, mouth ; e, stomach; i, intestine ; 

 <i, anus ; t, common stalk. The arrows indicate the direction of the current 

 of water serving for respiration. 



P 



