i".)() Aunals Entomological Society of America [Vol. Ill, 



Just caiidad of the point where the region of large cells gives 

 way to that of the tall slender ones, comes a group of cells which 

 during cictive secretion becomes greatly elongate and protrude 

 into the lumen. These cells are active in throwing off small 

 spherical bodies of their protoplasm by the pinching off of their 

 tips, which float out into the lumen to dissolve and form a 

 third supply of digestive secretion (Figs. 43 and 44, sec. p.) 



The fourth source of digestive secretion is the less elongate 

 epithelial cells farther caudad. These cells are more granular 

 and vacuolate next to the striate border and throw off distinct 

 globules which collect along the margin of the striate border 

 (Fig. 45, sec. g.) These globules seem to burst and give out a 

 secretion similar to the finely granular material of the anterior 

 part of the mid-intestine. The striate border becomes less 

 distinct where the cells are actively secreting and excreting but 

 is never completely obliterated. 



The mucous cells of Leidig ('57), Frenzel ('82 and '85), 

 Korotneff ('85), Beauregard ('8G), Fausseck ('87), Mingazzini 

 ('89), Balbiani ('90), and wSimpson ('00 in unpublished paper) 

 are present in this larva. They are scattered among the large 

 secretory cells of the anterior region as well as among the tall 

 slender cells of the posterior region. As compared with the 

 surrounding cells they are truly monsters (Fig. 46. m. c.) They 

 are connected wdth the basement membrane by a constricted 

 pedicle while the distal end is enormously expanded and pro- 

 trudes into the lumen. They are coarsely vacuolate throughout 

 but especially so toward the inner end. The nucleus is scarcely 

 larger than those of adjoining cells, and does not differ from 

 them in the arrangement of nucleolus and chromatin material. 

 Some writers have attributed to these cells the function of 

 secreting the peritrophic membrane, others claim that their 

 secretion serves as a lubricant. In the larva of Psychoda alter- 

 nata these cells certainly have nothing to do with the secretion 

 of the peritrophic membrane. The fact that the secretion of 

 these cells resembles that from surrounding cells microscopically, 

 that their greatest activity corresponds with that of the sur- 

 rounding cells and the fact that the food, enveloped in the peri- 

 trophic membrane, is continually floated, so to speak, in diges- 

 tive fluids, cause me to hesitate to accept the view that the secre- 

 tion of these cells is merely a lubricant. I am inclined to be- 

 lieve that here we have simpl}^ specialized digestive cells. 



