236 Annals Entomological Society of America [Vol. XIII, 



Just outside of the circular muscle layer scattered bundles of 

 long muscle fibres are found. This incomplete long muscle 

 layer is not different in character from that described for the 

 anterior crop. 



The Malpighian Tubules. 



The walls of the Malpighian tubules are made up of a single 

 layer of cuboid cells. The nuclei of these cells are large and 

 sometimes irregular. The cytoplasm is granular or alveolar 

 depending upon the phase of the secretion process. A well 

 developed intima is present in the cells. In certain places a 

 tubule may be made up of enormous cells placed end to end, 

 in which case there is a single large intracellular duct into which 

 drain numerous smaller ducts which ramify in the cytoplasm 

 in a lateral direction. 



At the point where the tubules enter the "internal gland" 

 there is an abrupt change in the character of their walls. They 

 become thin, the nuclei decrease in size and are less chromatic. 

 They retain this membranous character until they finally 

 empty into the intestine near the anterior margin of the "inter- 

 nal gland," at the junction of the ascending and descending 

 intestine. 



The ^^ Internal Gland." 



As previously explained, the name "internal gland" was 

 used by Lubbock in 1859 to denote the closely wound knot 

 formed by a part of the digestive tube in the thoracic region 

 of certain Hemiptera. The term is here used to designate the 

 complex formed by the ascending intestine and malpighian 

 vessels dorsal to the anterior crop. 



The ascending intestine, after running almost the entire 

 length of the abdominal cavity, in the' manner previously 

 described, begins a series of coils just above and closely apposed 

 to the dorsal wall of the anterior crop (Fig. 3). Immediately 

 before entering this coil the diameter of the tube becomes 

 somewhat enlarged and there appears to be much secretory 

 activity on the part of the cells of its epithelial lining for they 

 are much vacuolated both as to cytoplasm and nuclei and the 

 free ends of the cells become cast off into the lumen to a greater 

 extent than in the cells nearer the end where the tube originates. 



