316 Annals Entomological Society of America  [Vol. VII, 
the insects I have studied, and give more fully some notes 
regarding this process, and describing the epithelial cells. 
I shall consider, first, however, the Isopods, which are not 
insects but Crustaceans. 
Murlin, in an excellent paper on the digestive system of the 
Isopods, shows that here most of the digestive fluid is secreted 
in a separate organ, the hepatopancreas, the giant cells of which, 
however, pour out the secretion in much the same manner as 
those of the digestive epithelium of many insects. The Isopods 
have proved to be a very interesting and valuable group with 
which to begin such a study, both because of the simplicity of 
their organization, and ease of preparing material, and also 
because of the very large size of the cells. 
The Aptera, the lowest group of insects, will always be the 
source of a great deal of information regarding digestion, and a 
thorough study of such forms as Lepisma and Japyx would be 
valuable. Campodea, I found, has a digestive apparatus very 
similar to Collembola, as worked out by Folsom and Welles, 
even down to the apperance of the cells. Japyx (Fig. 1) is 
quite different. Here the mid-intestinal cells are very open, 
and have a somewhat alveolar appearance. The cell contents 
is irregularly granular, and contains numerous large clear 
vacuoles of varying size, which sometimes compose nearly the 
entire contents. Here and there are scattered dark granules 
which probably are concretions. The nuclei are small and 
basally situated, and stain almost black with iron hematoxylin, 
while in preparations stained with Ehrlich’s acid haematoxylin 
they are nearly invisible. The cells evidently arise from nidi, 
although the latter appear to contain more definite cells than 
is usual. The intima is very thin, and sometimes slight amounts 
of secretion may be observed in the digestive lumen along the 
intima. 
Lepisma has an extremely interesting digestive system, 
including a remarkable muscular crop, the posterior end of 
which protrudes into the mid-intestine. Here the same con- 
dition exists which Needham describes as occurring in the 
Odonata, but in lesser degree (Fig. 2). The active secreting 
cells, two to four in a group (s. c.) are very sharply marked 
off from the young, forming cells (y. c.), staining much darker, 
particularly with the iron hematoxylin stain. At the base of 
