REPRODUCTION 



185 



within the shme tube by the muscular contractions of the body of the 

 worms and finally are picked up by the seminal receptacles of the other 

 member of the pair. Transfer of sperms in the worm is supposed to be a 

 reciprocal act but it is not definitely known whether both worms dis- 

 charge sperms at the same time, or at different times during one copula- 

 tive act, or at different matings. While still bound together by the 

 mucous bands the worms may each produce a cocoon which surrounds its 

 body. This is accompHshed by the hardening of a secretion poured out 

 by the gland cells of the clitellum. The eggs are conveyed to the cocoon 

 by the slime tubes while the cocoons are 

 still in position about the clitellum. No 

 sperms are present in the cocoon at this 

 time. Sperms are discharged from the 

 seminal receptacles as the cocoons pass 

 their openings on segments 9 and 10, or 

 possibly are conveyed to the cocoons by 

 the slime tubes while the cocoon is passing 

 forward. Fertilization occurs after the 

 deposition of the cocoon. To deposit the 



cocoon the worm creeps backward out of the slime tubes and the cocoon. 

 Thus the cocoon is usually left surrounded by a part of the slime tube 

 (Fig. 143). As soon as the cocoon passes the head of the worm its elastic 

 ends contract and sharply close the openings. Development of the eggs 

 occurs within the cocoon. 



From observations by Miss Foot on worms in captivity it seems 

 that mating may be followed at intervals by the formation of several 

 successive cocoons. A slime tube (Fig. 144) and cocoon are formed much 

 as in worms that have just mated. The cocoon is formed about the 



Fig. 143. — Slime tube of the earth- 

 worm Helodrilufs faetidus with cocoon. 

 (After Foot.) 



Sli 



(a be 



Fig. 144. — Slime tube and cocoon in process of formation by a single worm. (After Foot 



and StrobcU.) 



cUtellum and the deposition of the eggs and sperms occurs as described 

 above. She found that Helodrilus fcetidus when kept singly in captivity 

 formed cocoons about every third day after mating, sometimes until as 

 many as 10 cocoons had been formed. At the close of this period the 

 clitellum was much reduced in size and the seminal receptacles nearly 

 empty of sperms. 



While in the earthworm and in some other hermaphroditic species 

 it seems that an elaborate mechanism insures cross-fertilization, in other 

 hermaphroditic species no such devices exist and, indeed, self-fertihzation 



