Vorhies—Larva ofPlatypliylax Designatus. 115 
The larger posterior portion of the hind-intestine can be read¬ 
ily divided microscopically into a large intestine and a rectum. 
In section the wall of the former is seen to be pouched or folded 
forward over the posterior end of the small intestine. The ep¬ 
ithelium of this part consists of a single layer of large, flat cells 
of considerable thickness, containing nuclei with finely granular 
contents., (Fig. 7.) The inner surface of these cells has a per¬ 
ipheral membrane of about the thickness of the peritrophic 
membrane of the mid-gut and of somewhat similar appearance, 
being marked with striae perpendicular to the surface. (Fig. 
8.) A constant layer of substance,—blue staining in haema- 
toxylin and in triple stain,—lies within the lumen. This makes 
it appear that the cells are secretory, but Yan Gehuchten, (8) 
who figures similar cells for the larvae of the Dipteron, Ptyckop- 
tera contaminata, takes the ground that they are exclusively ab¬ 
sorptive in function. Circular muscles are found within the 
peritoneum, but no longitudinal fibers. In the furrows between 
six irregular outfoldings or loose pouches of the large intes¬ 
tine lie six bands of longitudinal muscles, the latter being out¬ 
side the peritoneum. 
At the beginning of the last segment the character of the 
epithelium again changes abruptly and the lumen gradually be¬ 
comes vertical. The epithelium here also consists of a single 
layer of flat cells, but their size and thickness is much less than 
that of the cells of the large intestine. This portion is the 
rectum proper, though no accumulation of waste material is 
ever found within it, Within the anal aperture and extending 
out on the external surface a short distance is an area bearing 
strong, slightly curved chitinous teeth. Betten (1) apparently 
has overlooked this last division of the intestine. 
Spinning Glands. --The spinning glands of the larva of 
P. designatus are very well developed and have been found very 
interesting as regards the nuclear structures. The glands are 
about one and one-haJf times as long ns the body and lie ventrad 
and laterad to the intestine, each forming three principal folds, 
with the distal end lying in smaller curves of varying shape. 
(Fig. 12.) Each gland may be readily divided into conducting 
and secreting portions, a slight enlargement with a constriction 
