64 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



head and vibratile tail. They remain for some time attached by 

 their heads to the blastophor, but are finally liberated.* 



(2) Female Organs. The ovaries (0) are two pear-shaped 

 bodies, rather larger than the spermaries, and having a similar 

 position in segment 13. Their narrow ends are directed back- 

 wards. The oviducts (OD) are short, wide tubes, lying mainly in 

 segment 14, on the ventral side of which they open by the 

 female pores, much smaller than the male pores, but occupying a 

 similar position. Each oviduct ends internally in a funnel which 

 pierces the septum between segments 13 and 14, projecting into 

 the cavity of the former. The funnel communicates with a small 

 pouch-like ootheca (E,) (receptaculum ovorum), in which a few 

 ripe ova temporarily accumulate. The spermothecce (receptacula 

 seminis) are two pairs of rounded sacs, lying in segments 9 and 

 10 (S). They open laterally between segments 9 and 10, and 

 10 arid 11, just on a level with the lateral setae. 



The ovaries consist of germinal cells which develop into ova. 

 Each ovary contains many ova in different stages of development, 

 the ripest being at the free end. The ovum is spherical in shape, 

 and covered externally by a delicate vitelline membrane. The 

 granular protoplasm contains a clear germinal vesicle, with germinal 

 spot. The ripe ova burst out of the ovary into the body-cavity r 

 and are taken up by the ciliated funnels of the oviducts. 



Although the Earthworm is hermaphrodite, self-fertilization 

 does not occur. Two individuals copulate and fertilize each 

 other. This takes place on the surface of the ground during 

 the warm spring and summer months. The two. apply them- 

 selves by their ventral surfaces, their heads being in opposite 

 directions. Adhesion is effected by the slender genital setae, 

 the prominent ventral edges of the swollen clitella, and a firm 

 secretion of the clitella and capsulogenous glands. The sperms 

 pass back from the male pores of either worm to the spermo- 

 thecse of the other, along grooves visible at the time. They are 

 aggregated within the spermothecae into thread-like packets 

 (spermatophores), by means of a glutinous secretion. 



The ova are laid in firm capsules, probably formed by the 

 hardening of a- fluid secreted by the clitellum. In L. hercukus 

 many ova are passed into each capsule, together with a few 



* The contents of the vesiculoe commonly contain various stages in the life- 

 history of the Earthworm Gregarine, Monocystis lumbrici (see p. 17). 



