ANNELIDA : THE EARTHWORM, NEREIS 229 



worm, along a groove, into the spermathecse of the other, 

 after which the worms separate. The eggs are laid in a 

 cocoon, which is secreted by the clitellum as a broad band 

 round the body and passed forwards over the head. The 

 cocoon contains a nutrient fluid, and into it sperm which 

 has been received from another worm is transferred in a 

 little packet or spefmatophore. In passing over the head 



-p.v.s. 



Fig. 146. — A dissection of the reproductive organs of an earth- 

 worm. The dissection is made from above, and the median 

 parts of the vesiculas seminales have been opened on the 

 left-hand side. 



a.z'.s., Anterior vesicula seminalis ; a.v.s'., horns of the same; n.p.h., 

 nephridium ; o.v., ovary; p.v.s., posterior vesicula seminalis; 

 p.v.s 1 . , horns of the same ; r.ov., receptaculum ovorum (the funnel 

 of the oviduct lies immediately in front); s.p., spermathecse; 

 sp.r., sperm rosettes (funnels of the vasa efferentia); /., testes; 

 v.d., vas deferens ; v.ejf., vasa efferentia. 



the ends of the elastic cocoon close, and it becomes a small, 

 lemon-shaped body, which is left in the earth. Each cocoon 

 contains three or four ova, which are fertilised in it, but 

 usually only one completes its development. 



Earthworms have an extensive power of regeneration, 

 though it is not so great as that of Hydra. If the 

 body be cut in half, the head end will grow a new 

 tail, and the tail end, though more slowly, a new head. 



