116 



ANIMAL FORMS 



Fig. 69 the mouth soon leads into the esophagus, which 

 in turn leads into the crop that serves to store up the food 

 until ready for its entry into the stomach ; or in some of 

 the ants, bees, and wasps it may contain material which 



may be disgorged and fed 

 to the young. In many 

 cases the stomach is small 

 and ill-defined as in Fig. 69, 

 and again it may reach 

 enormous dimensions, near- 

 ly filling the body. It may 

 also bear numerous lobes or 

 delicate hair-like processes, 

 which afford a greater sur- 

 face for the absorption of 

 food. Behind the stomach 

 are a number of slender 

 outgrowths that are believed 

 to act as kidneys. Beyond 

 their insertion lies the in- 

 testine, which, like the 

 stomach, is the subject of 

 many modifications in the 

 different kinds of insects. 



The digested food is rap- 

 idly absorbed through the coats of the stomach and intes- 

 tine and enters a circulatory system which reminds us of 

 what exists in many of the Crustacea. The heart is situ- 

 ated above the digestive tract, and from it arteries pass out 

 to different parts of the body. Here the blood leaves the 

 vessels and is poured directly into the spaces among the 

 viscera, whence it is finally conducted through irregular 

 channels to the heart by its pulsations. 



In the Crustacea the blood is made to pass through a 

 respiratory system usually in the form of definite gills, and 

 the oxygen with which it is charged is distributed to all 



FIG. 69. Cockroach, dissected to show ali- 

 mentary canal, al. c. After HATSELEK 

 and CORI. 



