OF INSECTS. 133 



bags appended to its surface in certain tribes. They 

 produce the appearance of a coarse villosity, (PI. II. 

 fig. 2 dj) but when examined with the microscope, 

 they are found to be little bags, opening into the 

 ventricle. They are formed by the internal mucous 

 membrane, the other membranes not entering into 

 their composition. The greatest diversity of opinion 

 prevailed among physiologists respecting the func- 

 tional uses of these appendages, but it seems now 

 to be the most generally received opinion that they 

 are secerning organs, and that their secretions act as 

 solvents on the contents of the ventricle, particularly 

 when these consist of animal matter, for it is among 

 the carnivora that they are principally found. Other 

 appendages sometimes occur characteristic of par- 

 ticular races. 



The remaining portion of the nutrimental canal 

 may be called the intestine. It is always more sim- 

 ple in form, considerably narrower, and more deli- 

 cately constructed than the preceding divisions. The 

 slight expansions and contractions which it offers, in 

 certain parts of its course, have led sqpie to regard 

 it as consisting of nearly the same portions as the in- 

 testines of the vertebrata, and they consequently re- 

 cognise a duodenum, an ilium, a caecum, a colon, and 

 a rectum. If we were perfectly acquainted with the 

 functions of these organs in insects, as has been judi- 

 ciously remarked, it is possible that we might find 

 reason for these numerous divisions, each having a 

 special function allotted to it ; but in our present un- 

 certainty in this respect, we run less risk of error by 



