8 Transactions of the Society. 



of the colon is seen. In my figures of the ahmentary canal the 

 colon and rectum are extended into a horizontal position so as to 

 be seen. 



Nicolet in his drawing of the alimentary canal of Hoplophora 

 magna omits this portion of the canal altogether, but he gives one 

 enlargement of the hind-gut almost as large as the ventriculus ; this 

 enlargement I presume he intends for the rectum. I can only say 

 that I have not found such an arrangement in any of the 

 specimens of this or any other species which I have dissected; 

 indeed Nicolet's canal differs so materially from what I have met 

 with, that I should think that we were dealing with different 

 creatures, were it not that the species is an extremely well marked 

 one. The walls of the colon are far less thick and less muscular 

 than those of the ventriculus or rectum. 



The rectum (plate I. figs. 1, 2, 3, g) is usually pyriform, 

 sometimes very small where it arises from the colon, as in 

 HojjlopJiora magna, sometimes larger, as in Nothrus tlieleproctus, 

 but always distinctly divided from the colon by a sharp constric- 

 tion ; in some species, as Orihata imnctata, it continues small for 

 some little distance, gradually enlarging until near the anus, at, or 

 within a short distance of which, it is closed by powerful sphincter 

 muscles ; the actual anal end of the rectum is attached round the 

 opening on the ventral surface which is defended by the anal 

 plates ; a series of longitudinal muscles also arise from the posterior 

 parts of the rectum, and are inserted in the exo-skeleton near the 

 anal plates ; they doubtless assist in supporting the rectum and 

 holding it in its place, and probably also assist in defecation. 



The rectum itself is muscular, with the bands of muscle 

 arranged circularly ; this is very clearly seen in Nothrus theleproctus, 

 where, as in the last-named species, the constriction is some little 

 distance from the anal plates ; the portion of the canal between the 

 two is comparatively very thin and delicate. 



The Accessory Glands. — There are two conspicuous glands, not 

 I believe mentioned by any author, which I propose to call the 

 " preventricular glands " ; they frequently show like two black spots 

 through the dorsal surface, when at all transparent, particularly in 

 the nymphs, but they are seen equally well in the adults when the 

 chitin is not too opaque, and they appear to me to be always 

 present. When dissected out they are found not really to be 

 black but to vary in colour from deep yellow to dark brown. These 

 glands are shown in plate I. figs. 1, 2, 3, 4, y, and are seated on 

 the ventriculus at its extreme anterior part ; one on each side of the 

 oesophagus, just where it enters the ventriculus. The edge of 

 each gland is on the dorsal surface of the ventriculus ; so that, 

 from the dorsal aspect, they look globular, and often are so, but 

 more frequently they are somewhat flattened and show a tendency 



