314 Annals Entomological Society of America [Vol. VII, 
tinuous flow of digestive fluid. Haseman describes the larva 
of Psychoda as possessing this type of cells. It is also the type 
present in Lepidopterous larve, such as the silkworm (Fig. 11), 
or in the Coccide (Fig. 4), which after once settling down, 
remain attached to their food-plant, and continuously suck in 
the plant juices. A study of these cells makes it clear that, 
although no nests of nuclei are present from which the cells are 
replaced, nevertheless: the cells are replaced. Haseman has 
very carefully worked this out in the case of Psychoda and 
finds that the cells are replaced at the molting period. The 
old cells degenerate and slough off, and new ones, which he 
calls regenerating cells appear along the basement membrane. 
Haseman describes the growth of these cells, but makes no 
attempt to explain their origin. At once Adlerz’ notion of a 
basal protoplasmic network suggests itself. For, to judge from 
Haseman’s drawings the old cells degenerate completely and 
no part of them composes the new cells, except, as Haseman 
mentions, that some of the old material may be absorbed by 
these cells. We must look elsewhere, then, for their origin, 
and it is not incomprehensible that some sort of basilar proto- 
plasm may exist, from which these cells spring. My prepara- 
tions of the silkworm are unfortunately not numerous enough 
to show all stages of this degeneration and replacement, but 
it seems evident that it takes place here, in a measure as it does 
in Psychoda. Fig. 7 is from a sagittal longitudinal section of a 
young silkworm killed just before molting. There are many 
large, distended cells (d. c.) which appear to be pouring out 
their whole contents, but as none of these protruding droplets 
has ever been found detached, it seems more reasonable to 
suppose that the cells are degenerating, and that the protrusion 
is an artifact produced by improper killing. Between these 
cells are others (ab) with a basal nucleus and a clear lumen. 
This lumen I believe also has been produced artificially, but 
aside from this these cells are quite different from the others, 
and may perhaps be absorptive or mucous cells. Along the 
basement membrane are numbers of small cells (r. c.), each with 
a nucleus or occasionally two. These cells I take to be the 
regenerating cells. Fig. 8 shows a cross section near the base- 
ment membrane of this same epithelial layer. The three 
types of cells appear distinctly. 
