ZOOLOGY. 519 



freed as a separate and perfect intestine along with a 

 mouth and anus; the external wall appears as a free 

 tegument. But, seeing that two concentric and separated 

 cysts could not subsist without combination by means of 

 the nutritive system or the vessels ; a perfect vascular 

 system is formed, divided into veins, arteries, and hearts. 



The tegument, wherein the vessels become self-substan- 

 tial, is the branchial membrane. There is therefore placed 

 around the intestinal body a vascular body also, or 

 branchial membrane, which is consequently pleura or 

 mantle (pallium), as in the Mussels. The body of the 

 intestine consists of intestine and peritoneum; that of 

 the vessels of branchia? and pleura or mantle. 



These animals are hence bisystemic, being both Intes- 

 tinal and Vascular animals; but, since the vascular 

 system is a new addition, it is thus characteristic of the 

 circle, and its members must be therefore called Vascular 

 animals. With the vascular system, however, all its fur- 

 ther developments have been bestowed ; thus especially 

 the complication of the vessels with the intestinal ramifi- 

 cations or, in other words, the liver Hepatic animals. 

 The salivary glands also are a similar complication, and 

 in this series therefore they make their appearance. 



Lastly, the renal glands are such a kind of vascular 

 organ, or branchiae of the sexual parts ; they also begin 

 to be astir in this series. 



With the separation of the systems into separate 

 teguments or membranes, the sexual parts also separate. 

 The ovarium becomes an independent organ furnished 

 with its own excretory ducts ; the male parts are indi- 

 vidualized to form veritable testes furnished with excre- 

 tory ducts, or even with a penis. Still this is all 

 effected only by degrees, or as yet within the confines 

 of this circle. 



These animals divide according to the viscera into 

 Venous, Arterial, and Cardiac animals ; according to the 

 sexual parts, into Ovarial, Orchitic, and Renal animals. 



