PLATYHELMIA 



47 



the intestine. In D. hepaticum the branches of the intestine 

 permeate all parts of the body, and the products of digestion 

 are available at all points. 



Another highly developed tubular system is that of the 

 excretory organ. It begins in all parts of the body in hollow 

 cells or solenocytes, each furnished with a tuft of cilia, the 

 flickering action of which has suggested the name flame cell. 



Opening of vas deferens 

 Seminal vesicle 



Ovary 

 Vas deferens 



Testis 



Opening of oviduct 

 Uterus 



Shell gland 

 Vas deferens 

 Testis 



Yolk gland 



FIG. 20. Similar view to the preceding to indicate the relationships of the 

 various parts of the complicated reproductive system. 



The branches gradually anastomose until they reach a duct 

 which occupies the middle of the animal. This duct dis- 

 charges through a pore at the posterior extremity. This 

 kind of kidney is called a protonephridium, and is ectodermal 

 in origin. 



The nervous system is not very well developed, and it is 

 difficult to make out. A nerve ring surrounds the pharynx. 

 Two lateral ganglia are distinguished as swellings from which 

 nerves pass forward to the mouth and the anterior sucker, 

 and a pair of nerves which extend laterally to the hinder 

 aspect of the body. Two dorsal and two ventral nerves 



