ALIMENTARY CANAL, ETC., OF AMIURUS CATUS. 405» 
which the gastric epithelium is replaced at the pyloric valve by 
epithelium proper to the midgut. 
Edinger found in the carp these crypts surrounded by lymph 
vessels imbedded in the fibrille of the submucosa. Such has been 
my observations with these structures in the cat-fish. Soluble 
Prussian blue injected by means of a hypodermic syringe into the 
wall of the intestine, generally filled vessels of irregular size sur- 
rounding the crypts. 
The arteries of the intestine pass through the muscular layers at 
right angles and reaching the submucosa, the large branches run for 
a short distance parallel to the surface, and give off divisions which 
ascend into the mucosa and between the crypts. Their twigs then 
form meshes embracing the crypts. The capillaries run immediately 
under the superficial epithelium. Fine venous capillaries are con. 
tinued from these and unite as they progress towards the submucosa 
into larger branches. The arterial branches in the summit of a fold 
also form a connected mesh of fine capillaries. 
ENDGUT. 
The muscular walls of the endgut or rectum assume a thickness 
greater than in the midgut. The outer longitudinal fibres become 
arranged in separate bundles posteriorly which go to insert them- 
selves in the walls of the vent. The circular layer has a thickness 
relative to the longitudinal one proportionally greater than in the 
midgut. Large bundles from it grow inward carrying the sub- 
mucosa with them between the two surfaces of the valve separating 
the midgut and endgut. This acts as a sphincter muscle in making 
the valve tense. The folds of the mucous surface of the endgut are 
less conspicuous than they are in the midgut. They are fewer in 
number, narrow anid longitudinally arranged. No transverse furrows 
on these give the appearance of villi. The crypts are about as 
numerous as in the midgut, but narrower and longer. Crypts are 
present on both surfaces of the valve, and like its epithelium pre- 
sent transitional forms between those of the midgut and those of 
the endgut. 
The epithelium is constituted of cylinder cells not differing in 
shape from those of the midgut. They are, however, not so long, 
that is, the portion outside the nucleus is shorter, the peripheral wall 
is thinner, and appears to pass without clear distinction into the 
