2544 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 (esophagus, a tube of relatively small calibre, 

 continued back to the 15 th segment, where it en- 

 larges to form 



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

 segments 15 and 16. 



e. The oesophageal (calciferous) glands, three pairs of 

 lateral oesophageal diverticula, conspicuous by their 

 light yellow colour. The two anterior pairs arise 

 in segment 11 and the posterior one in segment 

 12. When fully formed, the anterior pair project 

 into segment 10. 



Puncture one of the glands — a milk-white fluid 

 will escape. Examine this under a low power, and 

 note the presence of carbonate of lime. (Cf. p. 243.) 



If any difficulty is experienced in following out the 

 oesophagus, it can be overcome by starting from the 

 crop and working forwards. 



/. 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 — 



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



