WORMS 



47 



egg cells. The reproductive girdle, or clitellum, already spoken of, 

 forms the case which is to hold the eggs (see Fig. 71). When the 

 sperm cells have been exchanged, and the ova are ready for fertili- 

 zation, the worm draws itself backward from the collar-like case or 

 clitellum so that this slips over the head. As it passes the four- 

 teenth segment, it collects the ova, and as it passes the ninth and 

 tenth segments, it collects the sperm cells previously 

 received from another worm. The elastic, collar-like 

 clitellum closes at the ends after it has slipped over the 

 worm's head, forming a capsule. The ova zxe fertilized 

 in this capsule, and some of them hatch into worms in 

 a few days. These devour the eggs which do not 

 hatch. The eggs develop into complete but very 

 small worms before escaping from the capsule. 



Habits. The earthworm is omnivorous. It 

 will eat bits of meat as well as leaves and 

 other vegetation. It has also the advantage, 

 when digging its hole, of eating the earth which 

 must be excavated. Every one has noticed the 

 fresh " casts " piled up at the holes in the morn- 

 ing. As the holes are partly filled by rains, the FIG. 78. 



r~, . , Side view, 



casts are most abundant after rains. The chief showing setae, 



enemies of the earthworm are moles and birds, 



. . pores, and 



The worms work at night and retire so early m reproductive 

 the morning that the very early bird has the P en ' n gs. 

 advantage in catching worms. Perhaps the nearest to 

 an intelligent act the earthworm accomplishes is to con- 

 ceal tJie moutJi of its hole by plugging it with a pebble or 

 bit of leaf. Worms hibernate, going below danger of 

 frost in winter. In dry weather they burrow several feet 

 deep. 



The muscular coat of the body wall is much thicker than 

 the skin. It consists of two layers : an outer layer of fibers 

 which run around the body just beneath the skin, and an 



