90 GENERAL BIOLOGY 



(a) The Male Organs. The sperm sacs, or seminal vesicles, 

 lying in somites ten to fourteen are large white organs, com- 

 posed of several lobes. In these the spermatozoa under- 

 go a portion of their development. There are two pairs of 

 spermaries or testes enclosed within the seminal vesicles, 

 but they are so minute as to render their dissection very 

 difficult. 



(6) The Female Organs. The sperm receptacles are two 

 pairs of spherical, whitish or yellowish sacs beneath the 

 sperm sacs, in the ninth and tenth somites. In these re- 

 ceptacles the spermatozoa received from another worm are 

 stored, and from them the sperms are passed into the egg 

 case in which the eggs are laid. The ovaries (one pair), 

 are small organs near the median line, attached to the 

 anterior septum of the thirteenth somite. They will be 

 rather hard to find. Posterior to them are funnel-shaped 

 openings which lead into the oviducts, and these in turn 

 open to the exterior at the fourteenth somite. 



Earthworms meet and pair at night in May and June, 

 and the sperm receptacles of each are filled w r ith spermatozoa 

 from the other worm. They separate and later the girdle 

 secretes a fluid which hardens and forms a tough cylindrical 

 membrane or cocoon about the body. The cocoon is moved 

 forward and as it passes the fourteenth somite eggs pass 

 into it, and at somites ten and eleven spermatozoa enter 

 and the fertilization of the eggs takes place. The cocoon 

 passes over the anterior end of the animal and drops to the 

 ground, the ends close and within this free capsule the develop- 

 ment of the young worms takes place. 



3. Digestive System. Carefully remove the sperm sacs 

 and the septa in the anterior portion of the body, exposing 

 the tube-like esophagus. Find the following parts : pharynx 

 (somites tw y o to five), esophagus (six to thirteen), crop (four- 



