PHYLUM ANNELIDA 205 



front end then moves forward. The setae at the front end 

 are next extended as those of the posterior end re with- 

 drawn and the longitudinal muscles by contracting pull the 

 body forward. Progress is continued by repeating such 

 activities. 



Though the earthworm is an indiscriminate feeder, it is 

 not without a discriminating sense of taste. At night 

 leaves and other parts of plants are pulled down into the 

 burrows (E), to be eaten later. If foods such as cabbage, 

 onion, and meat are placed on the surface of the ground 

 where worms are abundant and left over night, it will be 

 found that marked preferences are shown. Usually the 

 meat will be eaten first, then the cabbage, and finally the 

 onion. Hurwitz has recently shown that the chemical 

 sense in the earth worm's skin is more acute in some respects 

 than the sense of taste in man. He suspended worms over 

 different solutions so that they could be dipped in quickly. 

 By varying the strength of the solutions and recording the 

 time it took worms to withdraw from them a rather accu- 

 rate test was made. 



The alimentary canal of the earthworm is well suited to 

 extract the small amount of nutriment from the rather 

 indigestible soil. The soft, finger-like prostomium above 

 the mouth continually scrapes away particles so that they 

 may be sucked inside and swallowed by the muscular 

 pharynx. After passing the pharynx and esophagus, the 

 food is held in the large thin-walled crop until it can be 

 received for grinding in the tough gizzard. When thor- 

 oughly pulverized and mixed the mass enters the intestine 

 where it is digested with glandular secretions and absorbed. 

 The large amount of sandy grit in the food, though furnish- 

 ing little or no nourishment, helps to grind up organic 

 materials, just as the gravel does in a chicken's gizzard. 



The ccelom of the earthworm is not continuous, but is cut 

 off at the end of each segment by a membrane, or septum 

 (Fig. 16). The watery fluid in the body-cavity therefore 

 cannot pass freely from one end of the body to the other as 



