9 2 EARTHWORMS. 



susceptible to light. Each capsule is filled by several ova, plus 

 the sperm from the male receptacle. As a rule, only one ovum, 

 or a very few at least, develop ; the others die and shrivel up, 

 unless eaten, as they often are, by the embryo that hatches out. 

 This embryo eats not only the others, but it takes up all the 

 common mass of albumen. It then bursts its way out of the 

 capsule as a perfect worm, minus its sexual organs. Earthworms 

 grow by fresh segments being added posteriorly. The mature 

 female organs are two ovaries in the thirteenth segment and two 

 oviducts in the same, commencing in two ciliated funnels and 

 opening to the exterior in the fourteenth segment. On the 

 ninth and tenth segments are two pairs of sperm-reservoirs, 

 the receptacula seminis, which open between the ninth and 

 tenth and tenth and eleventh segments. These are full of 

 sperm during copulation. 



The male organs consist of two pairs of testes in the tenth 

 and eleventh segments, opening by an aperture on the fifteenth. 

 In the anterior half of the worm, over these sexual organs, is 

 formed in the breeding season a swollen band called the clitelhis. 

 Earthworms, although hermaphrodites, copulate : this act takes 

 place at night on the surface of the earth in June and July 

 to the greatest extent. The worms apply themselves ventrally 

 to one another, and lie in opposite directions, so that the open- 

 ing of the receptaculum sominalis of one worm is opposite the 

 clitellus of the other. During copulation the sperm flows back 

 along a longitudinal groove to the receptaculum of the other 

 worm. The ova produced as the result of the fertilisation 

 undergo unequal segmentation. 



Earthworms live most of their time underground, burrowing 

 to a great depth, often down to the subsoil : by so doing they 

 let in moisture and air, and loosen the subsoil to a considerable 

 extent, thereby doing much good. They draw down into their 

 burrows numerous leaves and other A'egetation, which they 

 devour in large quantities : they feed upon these lea'\'es during 

 the daytime, and draw them down at night. "We may often 



