Annulata. 93 



them. The first part of the digestive tube is the pharynx, 

 very muscular and thick-walled. Its own muscular fibers 

 enable it to close with considerable force. Attached to the 

 outside of the pharynx are muscles radiating in all direc- 

 tions to the outside of the body wall, by means of which the 

 pharynx can be retracted and dilated. The pharynx not 

 only serves in swallowing, but is the worm's only organ of 

 prehension. By means of the sucking and holding power 

 of the pharynx the earthworm is able to drag relatively 

 heavy leaves into the burrow. It is by the strength and 

 various movements of the pharynx that the worm performs 

 the work of burrowing. The pharynx extends back about 

 six segments. Back of the pharynx is the gullet, a slender 

 tube running to about the thirteenth or fourteenth segment. 

 Along the sides of the gullet are the esophageal glands, 

 whose limy secretion is supposed to aid in digestion. At 

 about segment fifteen the gullet dilates into the large, thin- 

 walled crop. Separated from the crop by a slight constric- 

 tion is the gizzard, which extends about two segments. 

 The walls of the gizzard are very thick and muscular, and 

 it has a tough chitinous lining. In it, by the aid of sand, 

 the worm grinds food, as the hen does by means of bits of 

 gravel, thus making up for the absence of teeth. Beyond 

 the gizzard, the intestine extends to the anus, which is a 

 vertical slit at the posterior end. The intestine is about 

 the same diameter throughout, except that it is constricted 

 at each partition, and bulges out in each segment. 



If a cross section of the intestine be made, it will be 

 found that the hollow is not circular, as would naturally be 

 expected from the external form, but is crescent-shaped, 

 with the concave side of the crescent uppermost. This is 

 due to a prominent ridge that projects downward from the 

 upper inner surface of the intestine. This ridge is called 



