64 



The Form of Insects 



Intestine. — At its hinder end the stomach leads 

 into the short, narrow, st7iall intestine whose structure 

 resembles that of the gullet and crop ; like those 

 organs and unlike the stomach, it is lined with chitin. 

 At the junction of the stomach and small intestine, 

 the kidney tubes, to be considered later, open. The 

 small intestine passes into the large intestine, the 

 front part of which, the colon, is coiled and has its 

 walls, lined inside with chitin, thrown into longi- 

 tudinal folds. The rectum, or hindmost part of the 



intestine, is also 

 lined with chitin 

 and its walls 

 show six pro- 

 minent ridges 

 projecting into 

 the cavity, due 

 to the folding 

 of the epithelial 

 layer which is 

 separated into 

 six d i s c o n- 

 tinuous bands, 

 so greatly bent 

 that triangular 

 spaces, wherein 



Fig. 45.— Cross section through Cockroach's rectum. l^CrVeS and ^air- 

 Magnified 50 times. From Miall & Denny. tubcS ramifv 



are present between the bands and the muscular layer 



(%• 45) (I)- 



Divisions of the Food-canal. — We have seen 

 that the front and hind regions of the food-canal — 

 the gullet, crop, gizzard, and intestine — are lined with 

 chitin, while the central portion (stomach) is not. 

 Thus there is a threefold division of the tube — a 

 fore-gut (stomodautn), including the guljet, crop and 



