THE ORGANS OP NUTRITION. 139 



the true ilium, which is however contradicted by its function, which, 

 like that of the caecum of the glires of the mammalia, subjects the 

 food to a second digestion and extraction before it is rejected. We are 

 convinced of this by the comparison of its state in the stomach, and 

 in this portion of the canal, for we find it here much more pappy than 

 there, but yet not so viscous as in the colon. 



109. 



THE COLON. 



The last division of the intestinal canal is called the COLON (PI. 

 XVII. XXII. H, H,). It is divided from the preceding portion of 

 the intestine by a valve which can completely shut its aperture. G. R. 

 Treviranus was the first to describe and figure it *. Its internal 

 surface, particularly near the mouth of the ilium, is thickly beset with 

 glandular warts or flocks, which are not found in the ilium itself. We 

 have observed glands only in the crop, and as their function there was 

 evidently the secretion of the first menstruum of the food, they may 

 here possibly produce a secretion to assist the rejection of the faeces. 



The COLON generally exceeds the ilium in size, but when the conical 

 or thick gut precedes it it is narrower ; but it then is even longer than 

 the ilium, which is not usually the case. The form of the COLON 

 varies, sometimes cylindrical, or clavate, or distended above (bees); 

 sometimes sack- shaped (Carabodca) , or longitudinally folded within 

 (caterpillars and the larvae of Calosoma). These folds are produced 

 by the internal intestinal membrane, and are either straight or waved, 

 and supported by horny ridges. The muscular membrane does not 

 assist to form these folds, but it is more compact and firmer than in 

 the preceding portions of the intestine, yet the above described thick 

 gut or occasional analogue (by situation) of the ilium is frequently 

 much more fibrous. The colon is also occasionally fenestrate, that is 

 to say, there are six ovate transparent spots in it which are surrounded 

 by a horny margin or edge, and form either one or two rows, varying 

 in situation, so that the spot in the lower I-OAV lies where in the upper 

 one is found the intervening space. This structure Suckow first 

 observed in the bees f. I found in Harpulus riijicornis a perfectly 

 similar structure of the colon, these fenestral spots were in the internal 



* Vcriuischtc Scliriftcn, vol. ii. p. 105. PI. XII. f. 3. 

 t In Hcusingcr Zeitschr. f. d. Org. Ph., vol. iii. PI. VI. 



