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 fibrillse 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 la}'er has a thickness 

 relative to the longitudinal one proportionally gi-eater 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 and 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 



