The Earthworm. 29 



segment behind, usually of a reddish colour, is a corresponding 

 sac belonging to the female system ; it is known as the recepta- 

 culum ovorum, or, better and more simply, as the egg sac,- or 

 ovisac. It seems, however, that, though this structure corre- 

 sponds to the sperm sacs, it has no important function. Finally, 

 there are two (or three or more) pairs of spermatheccR, oval to 

 spherical blind pouches opening on to the exterior by pores 

 lying between segments 9, 10 and 10, 11. 



The earthworm lays its eggs in cocoons, which are chitinous 

 structures fabricated by the clitellum. When formed they are 

 drawn over the head, the worm gradually withdrawing itself. 

 As they pass the generative orifices they receive ova and sperm 

 (the latter being derived from another individual, who deposits 

 it in the form of little cases sticking to the skin, the so-called 

 spermatophores), as well as albumen for the nourishment of the 

 growing embryos ; this latter is derived from glands — the 

 capsulogeiious or albumen glands — which are developed during 

 sexual maturity in the neighbourhood of the sexual organs. 



