60 THE EARTHWORM 



B. The Digestive System. 



The alimentary canal is a straight tube running from 

 the mouth to the anus, and is divisible into the following 

 regions. 



1. The buccal cavity is small, and is situated in the first 



three segments. The opening of the mouth in the 

 ventral part of the first segment has soft lips and no 

 teeth. 



2. The pharynx, which follows the buccal cavity, has thick 



muscular walls, connected with the body-wall by 

 strands of muscle which run obliquely backwards, 

 perforating the anterior septa. The pharynx extends 

 backwards about as far as the sixth or seventh 

 annulus when the animal is in an average condition 

 of extension ; but it lies entirely in front of the 

 septum dividing the fifth segment from the sixth 

 (fig. 16). 



3. The oesophagus is a straight tube extending from the 



pharynx to the thirteenth or fourteenth segment. 

 When the animal is not fully extended the oesophagus 

 appears dilated in each segment, and constricted 

 where it perforates the septa. 



a. The calciferous glands are a pair of short lateral 



diverticula of the oesophagus in segment x. At 

 certain seasons they contain concretions of more 

 or less crystalline calcareous matter, chiefly cal- 

 cium carbonate. 



To see these calciferous glands press aside the large white 

 vesicula seminales which hide them. 



b. The * cesophageal glands ' are two pairs of lateral 



protuberances on the sides of the oesophagus in 

 segments xi. and xn. They are hollow, and their 

 cavities, which are subdivided by a large number 

 of horizontal lamellae, do not open into the 

 oesophagus. 



