84 EARTHWORMS, LEECHES, AND SEAWORMS 



parts. If one be cut in two pieces, each portion, under 

 favorable conditions, is capable of reproducing the lost 

 part with its organs, thus producing two complete worms. 

 Moreover, the anterior half of one worm may be success- 

 fully grafted on to the posterior half of another. 



Its life history. — Each earthworm produces both sperms 

 and ova, but the ova are fertilized by the sperms from a 

 different individual. About the time the eggs are ready 

 to be laid, a band, or collar, is formed aroimd the clitellum 

 from mucus secreted by the glands of this organ. The 

 collar, which is gradually slipped forward, receives the ova 

 and sperms as it passes along and is finally worked off 

 over the anterior end of the worm. The collar now be- 

 comes closed at both ends and forms a horny capsule 

 containing the eggs. These capsules are deposited in 

 loose earth, or imder logs and stones, where they re- 

 main until the young worms emerge. Some of the eggs 

 in each capsule do not hatch but remain to furnish food 

 for the young worms produced from the other eggs. 



The distribution and habits of earthworms. — There are 

 many kinds of earthworms and they are found in all parts 

 of the world. They live in the earth in burrows varying in 

 depth from a few inches to several feet. They are noctur- 

 nal animals and spend the day hidden in their burrows 

 with the head lying near the surface if the ground is moist. 

 At night they come out in search of food, but usually remain 

 with the posterior end attached at the mouth of the burrow, 

 ready to disappear if danger threatens. They gather up 

 bits of leaves for food and collect pebbles to line the upper 

 parts of their burrows and to stop up the entrances after 

 withdrawing the body. As the ground becomes dry in 

 summer they burrow deeper and deeper into the soil and 



