CHARACTERISTICS OF THE DIGESTIVE APPARATUS. 



207 



intestine is short, nearly 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 



Pis. 61.— Digestive 

 Canal of the 

 Leech {Sanguisuga 

 medicinalis), after 

 Nuhn. , 

 oe, oesophagus ; v, stom- 



Fig. 62.— Viscera of a Caterpillar. {Rymer Jones.) 

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



ach; v t, caical appendages; glands ;'p, salivary duets; ABC, trachea; D E E E E, air-tubes ; F F F, epiploon 

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



