E PIT HE LI A. 279 



the setae ; some at the base of the larj^est are gigantic. The 

 cells which support the setas are termed trichogenic. 



Many of the epithelial cells beneath the cuticular skeleton 

 disappear entirely in the adult imago, others persist, and some 

 of these are pigmented with orange-brown or red pigment 

 granules. 



The cells beneath the cuticular lining of the stomodseum 

 and rectum in the imago are tesselated, except those of the 

 rectal papilla;, which are large, cylindrical, and probably 

 glandular (see Rectal Papillae). 



Mucigenic or Muciparous Cells are found in great numbers 

 in the metenteron. They resemble the goblet cells of 

 Mammals (PI. XVI., Fig. 13). 



The absorbent cells of the alimentary canal are probably all 

 mucigenic. They exhibit a more or less marked basilar border, 

 which in many Insects is so distinctly fibrillated that it re- 

 sembles a mass of cilia. This condition is well seen in some 

 sections of the intestine of the immature imago of the Blow- 

 fly, in which the basilar border splits into tufts, so closely 

 resembling tufts of cilia that they might easily be mistaken for 

 them, except that, when the living cells are examined, there is 

 no movement. In the adult insect the basilar border is much 

 thinner (see Alimentary Canal). 



Serous Gland Cells are seen both on the free surface of the 

 alimentary canal and in the salivary tubules in the imago. 

 They are distinctly striated like the cells of the pancreas, or 

 rodded like those of the kidney in Vertebrates. The cells of 

 the Malpighian tubules contain various granular substances, oil 

 and pigments, like those of the vertebrate liver (see Malpighian 

 Tubes). The cell-substance also frequently exhibits intracellular 

 channels. 



There are also small convoluted subcutaneous wax glands (see 

 Tracheal System), the cells of which are very small, but loaded 

 with fatty matter like those of sebaceous glands. 



Cell-fibrillation. — The cells, which intervene between the 

 muscles and the cuticular integument, of the long columnar 

 variety, are often palisade-like and undergo longitudinal fibril- 



19 



