III.] THE EARTHWORM. 255 



There is sometimes present a well-marked lateral 

 thickening of a highly vascular nature. 



j3. The gizzard. Note the great thickness of the 

 muscular wall of its anterior half. The cuticular 

 lining of the alimentary canal here attains its 

 maximum of development. 



y. The intestine. Note the lateral ingrowths of its 

 walls, developed metamerically at the points of 

 attachment of the mesenteric septa. In trans- 

 verse section they are seen to be refolded and 

 complex. 



2. Take the body of a second worm killed as directed at 

 the outset, but which has been subsequently pre- 

 served for 1 8 24 hours in alcohol. Pin it down 

 and dissect from the side. 



Make a median longitudinal section of the ali- 

 mentary canal, wash out its contents and examine 



a. The buccal sac and pharynx. The floor of the 

 former and roof and side walls of the latter are 

 both thickened and muscular. 



(3. The oesophagus. Its metameric constrictions 



are plainly visible. Look for the orifices of the 



calciferous glands. (Cf. p. 242.) 

 y. The intestine. Nofe the typhlosole, an immense 



median dorsal fold of the lining membrane of its 



roof; it is plicated laterally. 



Cf. the same in transverse section. 



Examine the lateral intestinal sacculations as 

 seen from within (Cf. i. h. y). 



S. Work over the relations of the whole to the 



