432 



THE INVERTEBRATA 



of an ectodermal stomodaeum or fore gut, an endodermal mid gut 

 and an ectodermal proctodaeum or hind gut. The fore gut consists of 

 (a) the buccal cavity succeeded by (b) the pharynx, which may be 

 muscular and form a pumping organ (Fig. 328 A), (c) the oesophagus, 

 which has a posterior dilatation, the crop. This functions as a food 

 reservoir and may have a diverticulum enormously developed in 

 sucking insects to store the liquid food. Lastly there is (d) the pro- 



mi. 



Fig. 304. General view of internal organs of Apis ?nellifica as seen from above ; 

 musculature and tracheal system not shown. From Carpenter, an. antenna; 

 bn. brain; co. colon; cr. crop; e. eye; ga. ganglion; ?ng. mid gut; 7nt. Mal- 

 pighian tubule; oe. oesophagus ; r?n. rectum; sa.gl. salivary glands (three types 

 are shown); pv. proventriculus ; il. ileum. 



ventriculus or gizzard, most typically developed in insects which eat 

 hard food as in the Orthoptera. The chitinous lining of the fore gut 

 is here greatly thickened and the sphincter muscles in this region 

 control the passage of food between fore gut and mid gut. Into the 

 buccal cavity discharge the salivary glands (Fig. 304), which may as 

 in the cockroach have a very similar function to those of the mammal, 

 in producing enzymes for the digestion of carbohydrates. In other 



