58 MAINE AGRICULTURAL EXPERIMENT STATION. ig02. 



The epithelial cells in the first two divisions of the mid-intes- 

 tine are especially active as secreting cells. Part of them are 

 filled with granules that are suspended in the protoplasm of the 

 cell, and others are quite free from these granules. In the pos- 

 terior divisions of the mid-intestine the epithelial cells are not so 

 large or high, but the arrangement of tissues is the same. 



In the hind-intestine the cuticula is very thick and the epi- 

 thelial cells are small and rather flat. The three inner layers of 

 the hind-intestine are thrown up into folds which are not very 

 noticeable in the anterior part, but are larger in the posterior 

 part. In the rectum the folds are very large and form the 

 so-called rectal glands. On the outside, in the depressions 

 between these ridges, there are six bands of longitudinal muscle 

 fibers. The rectum is larger than the rest of the hind-intestine, 

 and has thick muscular walls. The rectal glands probably have 

 no function as glands but are thought to be of use in closing the 

 intestine. 



SALIVARY GLANDS. 



The salivary glands, fig. 7, sg, are two in number. They are 

 situated in the dorsal region of the anterior part of the meso- 

 thorax, just in front of the anterior end of the mid-intestine, and 

 dorsal to the oesophagus. The glands are ovate in shape and at 

 their anterior ends give rise to a pair of small ducts which soon 

 unite to form a single median duct. This runs forward, just 

 dorsal to the oesophagus, and opens into the mouth near the oral 

 aperture. The glands are made up of a small number of large 

 cells, which are imbedded in a basement membrane of connective 

 tissue. The cells have large prominent nuclei, and may be seen 

 in different stages of secretion. Some are filled with granules 

 and others have the cell contents free from granules. The lumen 

 of the gland is small and irregular. 



The fluid secreted by these glands would seem, from the 

 position of the opening of the duct, to have little digestive func- 

 tion, but rather to serve as a lubricant for the mouth parts. 



EXCRETORY SYSTEM. 



The excretory apparatus consists of four large malpighian 

 tubules, fig. 7, mt, which open into the intestine at the junction 

 of the mid- and hind-intestine and extend as far anteriorly as 



