422 C. GORDON HEWITT. 



sally beneatli the heart to the posterior region, whei'e it 

 curves downwards, turns to the left, and runs forward for a 

 short distance, curving to the right, where it doubles back 

 transversely to the left. Here it doubles sharply back to the 

 right, fi'om whence it runs forward for a little way, and 

 crosses over to the left. Carving, it runs posteriori}^ to 

 become the distal intestine. Its walls are lined by an 

 epithelium of large columnar cells. 



The distal intestine {d.int.). The junction of this 

 with the proximal intestine is marked by the entrance of the 

 ducts of the malphigian tubes. It runs posteriorly, and 

 curves dorsally and forwards to become the rectum, from 

 which it is separated by a cone-shaped valve — the rectal 

 valve, the position of which is marked externally (fig. 21, X). 

 The epithelium of the distal intestine consists of small 

 cubical cells, which project into the lumen, and are covered 

 by a fairly thick chitinous intima. The epithelial wall of 

 the distal intestine is thrown into usually about six longi- 

 tudinal folds. 



The rectum (red.) is composed of three parts, an anterior 

 region, an intermediate region which is swollen to form the 

 rectal cavity, and a shorter region posterior to this which 

 opens externally by the anus. The anterior region is lined 

 by cubical cells, whose internal faces project into the lumen 

 of the rectum, and give the chitinous intima a tuberculated 

 structure. The intermediate region which forms the rectal 

 cavity contains the four rectal glands (rect.gl.). Its walls are 

 lined by a thin cuticle supported by a flattened epithelium. 

 The posterior portion of the rectum is short, and has thick 

 muscular walls. The cuticular intima is continuous with that 

 of the external skeleton. 



Salivary Glands. — There are two sets of salivary glands 

 — a pair of labial and a pair of lingual glands. The structure 

 of the labial glands will be described in the account of the 

 anatomy of the head. 



The lingual glands (fig. 17, sl.g.), though considerably 

 longer than the total length of the body, are of the simplest 



