162 



METAZOAN PHYLA 



distributed to the internal structures of the body and to the surface, 

 particularly to the head, which is the most sensitive region. Since the 



Oyar/ 



Yolk glands 



Oviduct 



Uterus 



Geniivjl atrium 

 vagina 



Testes 



Yasa efferentia 



Vas deferens 



Prostate gland 

 Seminal vesicle 

 Cirrus 

 Genital pore 



Fig. 79. — Reproductive system of a planarian. Somewhat diagrammatic. (From 

 Parker and Haswell, "Text-book of Zoology," after Jijima and Hatschek, by the courtesy of 

 The Macmillan Company.) The male organs are shown on the right side of the median 

 line, the female organs on the left, each being omitted on the opposite side. 



ganglia have connective tissue sheaths which more or less protect them, 

 they may be recognized as simple organs. The peripheral nerves also 

 have similar sheaths. 



The reproductive system (Fig. 79) is the most complex of all and most 

 fully justifies the term system. The male organs consist of numerous 

 spherical testes, which are masses of cells lying in the parenchyma. To 



