384 



CH^TOPODA. 



co-exist in the same segment with segmental organs (Lumbricidve). 

 In the earth-worm, whose generative organs were first accurately 

 described by E. Hering, the female apparatus consists of two ovaries 

 in the 13th segment,* and two oviducts, which begin with trumpet- 

 shaped openings into the body cavity, contain several eggs in a dila- 

 tation and open to the exterior on either side on the ventral surface 

 of the 14th segment. There are in addition in the 9th and 10th 

 segments two pairs of receptacula seminis, which open at the junction 

 of the 9th and 10th and 10th and llth segment respectively. They 

 are filled with sperm in copulation (fig. 310). 



The male genital 

 organs consist of 

 two pairs of testes 

 in the 10th and 

 llth segments, 

 and two vasa defe- 

 rentia, each of 

 which opens inter- 

 nally by two fun- 

 nels and to the 

 exterior in the 

 15th segment. 

 Copulation takes 

 place in June and 

 July on the sur- 

 face of the earth 

 at night. The 

 worms apply their 

 ventral surfaces to 

 one another and lie 

 in opposite directions, in such a manner that the openings of the re- 

 ceptacula seminis of one worm are opposite the clitellus of the other. 

 During copulation sperm flows out from the openings of the sperm 

 duct and passes backwards in a longitudinal groove to the clitellus, 

 and thence into the receptaculum seminis of the other worm. In 

 Tubifex and Enchytrceus the ovaries may break up into groups of 

 ova which float free in the body cavity. Special albumen glands 

 and also glands which secrete the substance of the shell of the cocoon 

 are often present. In the breeding season the above-mentioned 



* The head (prgestomium and buccal region) being reckoned as the first 

 segment. 



FIG. 310. Generative organs of Lumbricus in segments VIII. to 

 XV. (after E. Hering). T, Testes ; St, the two funnels of the 

 vas deferens on either side ; Vd, vas deferens ; OP, ovary ; Od, 

 oviduct ; Re, receptacula seminis. 



