254 ELEMENTARY BIOLOGY. [CHAP. 



The pharynx is marked off from the buccal sac 

 by a deep recess, in which the pear-shaped supra- 

 cesophageal ganglia are seen to lie. 



c. The oesophagus, a tube of relatively small calibre, 

 continued back to the i5th segment, where it en- 

 larges to form 



d. the crop, a spacious thin-walled sac, lying within 

 segments 15 and 16. 



<?. The cesophageal diverticula, 2 3 pairs, conspicuous 

 by their light yellow colour, lying within segments 

 i o to 12. In Allolobophora the posterior pair are 

 inconspicuous, the anterior pair (czsophageal pouches), 

 when examined in detail, opened up, will be found 

 to be reddish in colour and to alone open into the 

 oesophagus, the others (calciferous glands) opening 

 into them. 



Note the presence of carbonate of lime in the 

 latter (cf. p. 243). 



/. The gizzard, a pearly-white thick-walled sac, follow- 

 ing immediately upon the crop. It usually oc- 

 cupies segments 17 to 19. 



g. The intestine, a spacious yellow thin-walled tube, 

 extending back to the extreme end of the body. 

 The sacculations of its walls become less con- 

 spicuous as its hinder end is reached. 



h. Open up the crop, gizzard, and a small portion of 

 the intestine from above, wash out the contents 

 and note 



a. The crop. Its walls are thin and membranous. 



