88 INVERTEBRATE ZOOLOGY. 



Testes. These are beneath the spermatic vesicle and are exposed 

 by removing the dorsal wall of the vesicle and taking ont its 

 contents. They may then be seen as two pairs of little solid 

 white organs, lying upon the sides of the nerve cord (10, 11). 

 Their cells pass by some unknown way into the spermatic 

 vesicle, in which they develop. 



Vasa deferentia. Slender tubes, beginning with two pairs of 

 funnel-shaped openings just posterior to the testes (10, 11). 

 Upon each side the two tubes unite into one (12), thus form- 

 ing two lateral vasa deferentia, which open externally (15). 

 The funnels collect the ripe spermatozoa which escape from 

 the spermatic vesicle by an orifice communicating with the 

 coelom. 



(b) Female. 



Spermotliecae. Two pairs of spherical sacs, used to contain the 

 spermatic fluid of another individual, received diiring pair- 

 ing. The eggs are fertilized by this fluid and not by that of 

 the same animal. They lie upon the ventral wall (9, 10) and 

 open separately between the segments (9-10) (10-11). 



Ovaries. A pair of very small organs, lying upon the ventral 

 wall (13) on each side of the nerve cord. The mature eggs 

 break loose and float about in the coelomic cavity until col- 

 lected by the oviducts. The ovaries are scarcely visible ex- 

 cept when mature. 



Oviducts. Two little tubes, which begin as funnel-shaped open- 

 ings in the dissepiment between (13) and (14). These collect 

 the eggs and open externally in (14). 



3. Circulatory System. 



The blood is red (colored plasma, white corpiiscles) and thus the ves- 

 sels are easily traced. It is a closed system, entirely separate from 

 the coelom. 



Longitudinal vessels. These are five in numl)er. (1) median dor- 

 sal, (2) median ventral, (3) sub-neural, (4) and (5) a pair of lat- 

 eral neural vessels. The blood flows in an anterior direction 

 in (1), posteriorily in the others. 



