296 



THE EARTHWORM AND OTHER ANNULATA 



iacles, in segments nine and ten, may be regarded as a part 

 of the female system, since they receive the spermatozoa that 



Q 



E 



a 



H 



F:g. 143. — Reproductive organs of earthworm. 



A, an ovary with ova in various stages of growth. B, a single ovum, on a slightly larger 

 scale than the ovum shown in A, about ready for detachment from ovary. C, an egg 

 capsule (r/. Fig. 147 C). D, dorsal view of reproductive system with seminal vesicles of 

 right side dissected to show testes and sperm funnels. E, multinucleated cell that is detached 

 from the testis and develops into spermatozoa within the seminal vesicles. F and G 

 . development of spermatozoa, showing the spermatids, on the surface of a central mass 

 of cytoplasm from the original multinucleated cell {E). H, two spermatids in a later stage 

 as they appear attached to the surface of this spherical mass of cytoplasm. 



bl, muscular bladder-like portion of nephridium; /, funnel or nephrostome of nephrid- 

 ium; n.c, ventral nerve cord; ne, nephridium; od, oviduct; ov, ovary; s.o., receptacle 

 of oviduct; s.f., sperm funnel; s.r.l. and s.r.2, seminal receptacles; a.v.l, s.v.2, and s.d.3, 

 seminal vesicles; t, testis; v.d., vas deferens; v.e., vas efiferens. 



are obtained from another worm during sexual union and used 

 in the fertilization of the ova at the time of egg laying. 



