246 



GENERAL ZOOLOGY 



gether for about one third of their length, with the "heads" 

 pointing in opposite directions. This position brings each 

 worm in a position such that the small openings which lead 

 into sperm-receiving sacs (seminal receptacles) are in con- 

 tact with the openings of the male reproductive organs of the 

 other individual. Each worm expels a quantity of its sperm 

 into the seminal receptacles of the other. In these recepta- 

 cles the sperm is retained until the eggs are ready to be laid. 



n 

 m 



A B C 



Fig. 130. Egg capsule, egg, and spermatozoon, of earthworm 



A, egg capsule; B, egg with nucleus; ov, eggs; C, spermatozoon: n, nucleus; 



m, middle piece ; t, tail * 



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

 page 239, 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 band about the clitellum. The 

 band of mucus is then moved forward slowly. At the four- 

 teenth somite the eggs are caught up from the oviduct, which 

 forces them out, at the time the band, or capsule, passes. 

 Farther forward the sperm that has been stored in the semi- 

 nal receptacles is received into the capsule. At the anterior 



1 From Sedgwick and Wilson's General Biology. 



