770 Wisconsin Academy of Sciences, Arts, and Letters. 
Sections through this narrow part of the ileum show the 
wall to he folded and that the folds may nearly close the 
lumen. A longitudinal section (fig. 29) shows the folds to be 
more numerous in the posterior part. At two different places 
there is a larger number of circular muscles than usual (fig. 
29, cm). The more anterior of these two groups of muscles 
is the larger and would, in contraction, close the opening be¬ 
tween the ileum and the rectum; the more . posteriorly sit¬ 
uated group would have the same action. 
The large cells mentioned as occupying three areas in the 
ileum are not sharply marked off from the regular epithelium 
but the one kind passes gradually into the other. The smaller 
regular epithelial cells (fig. 30) show no peculiarities; the cy¬ 
toplasm is slightly vacuolated and longitudinal striae were 
noticeable in the cells. In the large cells (fig. 31) this stri- 
ation, (Sadones, 24), was more apparent; in them the nucleus 
was large and irregular and it generally showed a massing of the 
contents in that half nearest the lumen of the ileum. As 
Faussek (10) says, so great a difference in the structure of the 
cells must signify some physiological difference and a cytolog- 
ical study of the ileum during different periods of nutritive 
and other activities would no doubt lead to interesting results. 
The presence of these large cells in the ileum has been ob¬ 
served in other insects. 
The rectum, 2mm in length, extends through the posterior 
half of the ninth and the tenth segment. Except for a short 
distance at either end, where it is slightly narrower, it is 
straight and of equal diameter throughout. In external view 
the rectal glands are seen to occupy nearly all the surface, 
they appear as six wide longitudinal areas with narrow, darker 
space's between. The difference between the two parts, rec¬ 
tal glands and intermediate space, does not show as plainly 
as in most insects, as here the latter spaces are nearly covered 
by the rectal muscles and thus in part hidden. The six rectal 
glands begin near the anterior end of the rectum and continue 
to within a short distance of the anal opening (fig. 26, Rt.). 
