276 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



projecting folds, formed by delicate epithelial cells ; the folds resemble 

 somewhat those that are found in the caeca of sharks, for instance. 



The lining membrane of the ventricle is formed by cylindrical cells, 

 which form little glands, separated from one another by walls of con- 

 nective tissue, in a manner the details of which are reserved for my 

 final report. The posterior limit of the stomach is marked by very pe- 

 culiar structures, which, to my knowledge, have never before been 

 described. They are particularly interesting because they present pe- 

 culiarities which are not otherwise united in one organ. They are folds 

 which project forward, twelve in number, and encircling the cavity of 

 the intestine. When I first discovered them, I thought that I must by 

 some mistake have examined, not the intestine, but the terminal por- 

 tion of the digestive tract, where somewhat similar organs are found, 

 and have long been known under the name of rectal glands {Rectal- 

 drUsen), The intestinal folds are sharply limited, each with a convex 

 border anteriorly, while posteriorly they gradually fade out. They are 

 covered by large cylindrical cells, which in some cases are completely 

 filled with pigment granules. These singular folds are found in the 

 same position in Caloptenus spretus and C. femur-ruhrum as in (Edipoda 

 sordida, and their character is essentially the same in the three species. 

 I anticipate that they will be found to occur in the grasshoppers and 

 locusts generally, and perhaps even in many other insects. 



Behind the folds, the intestine still continues straight onward in its 

 ccurse for about three segments. The histological character of this 

 portion is singular, inasmuch as the epithelial cells which form its lining 

 are of various sizes, some of them being large and others small, those of 

 the same size forming longitudinal bands and slight folds. Next follows 

 the colon, which ascends backward in a nearly straight line. Its 

 lining membrane is thrown up into irregular folds, and has a brownish 

 color. There is, however, no cuticula, as in the crop. These folds 

 probably serve mainly as a filter, and to retain the food until the 

 digestible part is absorbed. 



The whole of the digestive tract between the proventricle and the 

 rectum, that is to say, the ventricle, diverticula, intestine, and colon 

 together, completes the process of digestion, and carries on that of 

 absorption. In what manner this absorption is accomplished is still 

 unknown. 



The rectum is nearly straight and horizontal in its course, except 

 terminally, where it turns upward to form the dorsally placed anus. It 

 varies in size according to the amount of matter accumulated in it. It is 

 especially characterized by the presence of six broad, longitudinal folds, 

 and by tbe marked development of its muscular walls. In it the last 

 traces of moisture in the digested masses are apparently absorbed, after 

 which the ball is expelled through the vent. The rectum represents the 

 fourth and last of the physiological divisions of the digestive tract. 



The composition of the walls of the intestinal canal is essentially upon 



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