LESSON 38.] 



NUTRITION IN INSECTS. 



137 



it narrows to a size scarcely larger than the stomach, and slightly 

 enlarges again, prior to its termination. 



The gastric teeth (Figs. 224 and 225), are shown in two views of 



FIG. 224. 



\\\:\ I 1 _IY ! '*i ! r/l ' 



Gastric teeth, Cockroach. 

 FIG. 226. 



FIG. 225. 



Pavement e 

 cav 



pithelium of funnel-shaped 

 dty, B. Americana. 



Gastric teeth, B. Americana. 



FIG. 227. 



them. In the first (Fig. 224) r the crop has been cut open, and the 

 teeth seen in profile, whereby their entire figure is well shown. The 

 central teeth show their toothed processes very distinctly ; the lateral 

 teeth are somewhat foreshortened, and not quite so perfect. It will be 

 seen that the upper portion of these teeth is terminated by a long 

 and strong toothed process ; the lower portion also is indented, and 

 toothed, the whole forming a most efficient apparatus. 



Moreover, they are based upon and supported by a series of bones. 



In Fig. 225, the spectator looks down upon the teeth, and into 

 the funnel-shaped, valvular cavity beneath them. The teeth are 

 seen at a; strong fasciculi of muscles be- 

 tween them at b, and the membrane which 

 lines the funnel-shaped cavity, leading to the 

 stomach, is thrown into a number of large 

 rounded folds, c. This membrane is covered 

 with a beautiful surface of minute pavement 

 epithelium (Fig. 226). 



621. A preparation, showing the salivary 

 glands entire, is figured in 227. The lob- 

 ules (b) are everywhere seen communicating 

 by short ducts, with the large duct common to 

 the glands on either side (&); the latter 

 coalesce, and form a common duct which emp- 

 ties its secretion into the mouth (c). 



Salivary glands, B. 

 Americana. 



