118 



GENERAL PRINCIPLES OF ZOOLOGY. 



special outlets are superfluous, since the rij^jc elements can reach 

 the exterior directl]? by rupture of their covering or by means of 

 the digestive tract. 



Germinal Epithelium and Germinal Glands. — Male and female 

 sexual cells, as we have seen, originate from an undifferentiated 

 incipient organ, or anlage, which is called the germinal epithelium. 

 Usually it forms a part of the epithelial lining of the body cavity, 

 in many animals jiermanently, in others only temporarily; in the 

 latter case it separates, usually by constriction, and forms gland- 

 like bodies, the gonads or sexual glands. 



Gonochorism and Hermaphroditism. — In most animals the 

 germinal epithelium produces either only female or only male 

 sexual cells; such animals are called separate-sexed, dicecioxtfi or 



im bzy M 





^~\~z^d 



dzy ozf- 



Fig, 71. — Sexnal m-Ljajis of f^Kinhrinix auricula. (From LaiiK, after Voct and Yimff.) 

 The seniiiial vesiclt.'H {if the ri^hf side afe removed, ^jm, \'eiitral nerve eoi'd; /')• 

 and /»/, ventral and lateral rows of seta?; .sC, si", receptaeula seminis: sU>, !<h'\ .s/i^, 

 the tliree seminal vesicles of the left side, which are connected with a tnedian 

 unpaired seminal capsule {shu). Enclosed in the latter are the anterior and pos- 

 terior testes (/)', //=), and tlie anterior and posterior seminal funnels (M. i-), "which 

 lea.d into the vas deferens (nl). o, ovaries: /o, ciliated fnnitels leading into the 

 oviducts (OP); di, dissepiments; VlU-XV, eighth to htteentli segments'. 



r/onorhoristif\ in opposition to the licDiutphrodific forms, in which 

 both kinds of sexual ghinds are contained in one and the same 

 iiidiviilual. DiflVrent degrees of henmiphroditism can be distin- 

 cuislied ; comnionlv testes and ovarv are ci)iita.ined in the same 



