EARTHWORM. 219 



for in Polychaetes the genital products mature in the general 

 body cavity, just as the spermatozoa in the earthworm 

 mature in the seminal vesicles. 



(3) From the seminal vesicles the spermatozoa are carried 

 to the exterior by means of the vasa deferentia. The in- 

 ternal openings of these are large and funnel-shaped, and 

 are concealed by the seminal vesicles. Each of the four 

 funnels opens into a duct, and the two ducts unite at each 

 side to form the two elongated vasa deferentia, which pass 

 backwards to open externally on the i5th segment. 



(b) The Female Organs consist of two ovaries and two 

 oviducts, each of which has a side receptacle for the eggs. 



(1) The two ovaries are small bodies situated near the 

 nerve-cord on the septum between segments 12-13. Each 

 is pear-shaped, the stalk of the pear being a string of ripe 

 ova. They are more readily seen than the testes. 



(2) The two oviducts open internally on the anterior 

 face of the septum between 1314, and externally on the 

 ventral surface of segment 14. Into the wide ciliated in- 

 ternal mouths, which lie opposite the ovaries, the ripe eggs 

 pass. 



(3) The egg-sac or receptaculum ovorum, near the internal 

 mouth of each oviduct, is a posterior diverticulum of the 

 septum between segments 13-14. Within it a few mature 

 ova are stored. 



(c) Two pairs of receptacula seminis or spermathecae 

 receive spermatozoa from another earthworm, and liberate 

 them to fertilise the eggs of this one. They are white 

 globular sacs, opening in the grooves between segments 

 9-10 and 10-11, and probably, like the genital ducts, arise 

 from modified nephridia. According to some, these sper- 

 mathecoe not only receive and store spermatozoa, but make 

 them into packets or spermatophores. Others say that the 

 glands of the clitellum make these packets. At any rate, 

 minute thread-like packets of spermatozoa are formed, and 

 a pair of them' may often be seen adhering to the skin of 

 the earthworm about the saddle region. 



When two worms unite sexually, they lie apposed in 

 opposite directions, the head of the one towards the tail of 

 the other. What happens is that the spermatozoa of the 

 one pass into the receptacula of the other. 



