THE EARTHWORM 165 



erens. At the junction between the ninth and tenth, and 

 between the tenth and eleventh segments, may be found two 

 pairs of white sacs, each opening to the exterior by an opening 

 at the junction line between the segments. These are the 

 seminal receptacles, sr, and their function is to receive the 

 secretions from the seminal glands in copulation. 



Copulation and Egg Laying. Although the earthworm is an 

 animal producing both male and female elements in the same 

 individual, the habits of the animal are such that there is no 

 fertilization of the egg by the sperm of the same individual 

 that produces the egg, but a cross fertilization always occurs 

 between two individuals. At the breeding season, which is 

 early in the summer, two individuals place themselves side by 

 side with their heads in opposite directions, and by means of the 

 secretions from the glands in their skin there is formed a slimy 

 covering that holds the two individuals in close contact (copu- 

 lation). In this position, each transfers sperm material (see 

 Chapter XII) from its sperm glands into the seminal receptacles 

 of the other, after which they separate. During copulation, 

 or immediately afterwards, a secretion is produced by the cli- 

 tellum, which forms a band around the animal that extends 

 from the twenty-eighth to the thirty-fifth segment of the body. 

 At the close of copulation, after the animals have separated, 

 this band is gradually pushed forward until it finally slips off 

 over the head. As the band passes forward over the fourteenth 

 segment a certain number of eggs are extruded into it from the 

 oviduct; and when it passes over the ninth and tenth segments 

 some of the sperm material from the seminal receptacles is 

 also ejected into it. As it passes off over the head it closes 

 up by its own elasticity. Inside of this band the eggs of each 

 individual are thus mixed with the sperm from the other indi- 

 vidual and cross fertilization occurs. This case holding the eggs 

 and sperms is now known as a cocoon, and within it the 

 eggs develop into earthworms. The cocoons are deposited in 

 the soil and may be found early in the summer. 



