164 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
as food reservoirs. Other investigators record the detection of blood 
in the sacs of the mosquito and the similar pouches developed in 
other flies occasionally contain food. In view of these facts there 
seems to be no good reason for denying that these diverticula serve 
as storage places for food. The name “food reservoirs” (Nuttall 
and Shipley, : 01-: 03) or “esophageal diverticula” (Granpr4 and 
Charmoy, : 00) should replace the older and misleading terms “ aspi- 
ratory vesicles,” “suctorial vesicles,” etc. 
When one of these diverticula is extracted and is examined under 
a microscope, the only structure noted at first is an irregular and vary¬ 
ing mesh of delicate striae. More careful study makes it clear that 
these “striae” are wrinkles or folds of the delicate intima that lines 
the pouch, varying in size and position with the torsion or tension of 
the particular part under observation. By staining the fresh tissue 
with Bismark brown, distinct muscle fibers become visible and the 
nuclei of the epithelium appear (pi. 16, fig. 42). With a oil- 
immersion lens the epithelium itself can be distinguished in places as 
a granular cloud. Whether the muscle bands have as regular a dis¬ 
tribution with Culex as the similar bands described by Nuttall and 
Shipley on the ventral sac of Anopheles, was not determined. The 
“ striae ” sometimes pass across a muscle without alteration, but usu¬ 
ally, of course, they are more numerous along the line of the muscle, 
interlacing and radiating in groups from its borders. Under a low- 
power lens this gives them a strong resemblance to muscular fibrillae. 
The appearance vanishes when a higher magnification is used, but 
should be noted, since, with some reagents — e. (/., metliylin blue — 
the color fills the “striae,” seemingly staining them. If a pouch is 
torn the excessively wrinkled intima gives a fibrous appearance 
to the fragments. This is probably the basis for Giles’ assertion 
that these organs are composed of finely branched tracheae. “The 
fibers are neither more or less than extremely elastic and disten- 
sible tracheae, which swell out into bubble-containing dilatations. 
. ... Apart from a few loose connective elements the sacs consist 
of nothing else than .these curiously modified tracheae.” In connec¬ 
tion with this statement with respect to structures that are obvious 
diverticula from the esophagus and have a less extensive tracheal 
supply than any other part of the alimentary canal, except possibly 
the pharynx and antlia, Giles also holds that there are two ventral 
sacs, that there is no organic connection between the esophagus and 
