SALIVARY GLANDS 39 



is marked externally (fig. 14, 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 throNvn into usually about 

 six longitudinal 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, w'hich 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 (p. 63). 



The Lingual Glands (fig. 12, sl.g.), though considerably longer 

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

 type. They are of uniform width throughout their whole length, 

 except the slightly swollen blind termination. These blind ends 

 lie one on each side of the ventral and posterior region of the 

 abdomen, generally embedded in the fat body. They take a 

 sinuous course forwards through the abdomen into the thorax, 

 where they run alongside the ventriculus. At the sides of the 

 proventriculus they are thrown into several folds, wdiich appear 

 to be quite constant in character. They pass forwards at the 

 sides of the oesophagus, and on entering the cervical region 

 the ducts lose their glandular character and assume a spiral 

 thickening; before leaving the cervical region the two ducts 

 unite below the oesophagus, and the single median duct enters 

 the head ventral to the cephalothoracic nerve cord and runs 

 direct to the proximal end of the hypopharynx, at the end of 



