266 ANIMAL BIOLOGY. [Part II. 



This succeeding portion is the chylific stomach (ve.), constituting 

 the mesenteron or mid-gut of the canal. At its anterior end there 

 are eight ccecal tubes (cce.), which have been regarded as a diges- 

 tive gland, but are more probably diverticula of the chylific 

 stomach, the lining cells of which have taken on the function of 

 secreting a feebly acid fluid, which has the digestive properties 

 of the pancreatic juice of vertebrates. The epithelial cells of 

 the chylific stomach (in which there is no chitinous lining) are 

 very probably absorbent in function. 



Marking the junction between the mesenteric and proctodseal 

 segments of the canal, but properly belonging to the latter, are 

 a number (sixty or more) of long thread-like Malpigliian tubules 

 (m. t.)j inconspicuously grouped into six clusters. They are 

 lined with large epithelial cells, within which are found crystals 

 containing uric acid, and said to consist of urate of sodium. 

 Similar crystals are found in the lumen of the tube. The Mal- 

 pighian tubules are therefore undoubtedly excretory in function. 

 In another part of the body, however namely, in the fat lody 

 (corpus adiposum), which appears as a white cellular mass sur- 

 rounding the viscera when the cockroach is dissected crystals 

 containing uric acid have been found. It is conjectured that the 

 urates here elaborated escape by the blood which bathes the 

 perivisceral cavity, and are again taken up by the Malpighian 

 tubules, to be thence finally discharged into the intestine. 



Posterior to the Malpighian tubules is the short, narrow, small 

 intestine orileum (il.), which is separated by an annular fold from 

 the more dilated colon (co.). This narrows and becomes somewhat 

 constricted before it passes into the rectum (r.). The rectum is 

 characterised by six longitudinal folds with largely-developed 

 epithelium cells, beneath which are tracheal tubes. Between the 

 longitudinal folds the epithelium is much thinned or absent. 

 Posteriorly the alimentary canal opens by the vent, whence the 

 inflected cuticle passes inwards to line the proctodaeal portion 

 of the canal (rectum, colon, and ileum). A transverse section 

 of the stomodseal or proctodseal segment of the canal shows 

 internally the chitinous lining, followed by an epithelial layer, 

 external to which is a muscular layer with circular and longi- 



