CHAKACTEKISTICS OF THE DIGESTIVE APPAKATUS. 



207 



intestine is short, nearty straight, and simple ; sometimes it is also pro- 

 vided with caeca. In insects there is a great variation in the form and 

 length of the canal, depending on the stage of metamorphosis ; nearly 



FIG. 61. DIGESTIVE 

 CANAL OF THE 

 LEECH (Sanguisuga 

 medicinalis), AFTER 



NUHN. 



oe, oesophagus: v, stom- 



FIG. 62. VISCERA OF A CATERPILLAR. (Rymer Jones.) 

 GH. oesophagus: HI, stomach; IM, intestine: K, biliary vessels: QR, salivary 



ach; vt, cascal appendages; glands: P. salivary ducts; ABC, trachea; D E E E E,' air-tubes ; FFF, epiploon, or 

 r. rectum ; a, anus. fat-mass ; V X Y, cjeca. 



