210 



GENERAL ZOOLOGY 



The presence of the thick band, the clitellum referred to on 

 page 196, indicates that the individual is sexually mature. 

 The clitellum is provided with glands on its ventral surface. 

 Just preceding the time of egg-laying these glands secrete 

 a thick mucus which forms a ring about the clitellum. Into 

 the space between this ring and the body is poured a milky 

 secretion which is food for the young earthworms. The ring of 

 mucus is then moved forward slowly. At the fourteenth somite 

 the eggs are caught up from the oviduct (Fig. 100, 36), which 



ov 



A B C 



FIG. 103. Egg-capsule, Egg, and Spermatozoon, of Earthworm 



A, egg-capsule. B, egg with nucleus: ov, eggs, about natural size. C, spermato- 

 zoon: n, nucleus; w, middle piece; t, tail 



(From Sedgwick and Wilson's General Biology) 



forces them out, at the time the ring passes. Farther forward 

 the spermatozoa that have been stored in the seminal recepta- 

 cles are received into the ring, and while the ring is making 

 its way forward, fertilization, which consists of the union of 

 the spermatozoon with the egg, takes place. At the anterior 

 end the ring begins to draw together at the ends, and when 

 this egg-capsule (Fig. 103, A) has been pushed off, it is a short, 

 spindle-shaped, tough-coated sac, about as large as a grain of 

 wheat, inside of which all the eggs are fertilized. Few of them, 

 however, reach the stage of young, free-moving earthworms. 



