ALIMENTARY CANAL, ETC., OF AMIURUS CATUS. 403 



relaxed intestine. A partial distension of the midgut with chromic 

 acid and alcohol easily demonstrates the connected character or con- 

 tinuity of these prominences as longitudinal folds. 



The musculature consists of an outer longitudinal layer with an 

 inner one of smooth fibres. The latter is the thickest, and in the 

 pyloric valve increases so as to form the constricting muscle. 



The nmscularis mucosae is but a thin layer compared to that of 

 the stomach, and is formed of smooth fibr.es. The submucosa is very 

 much supplied with fissure-like cavities which are part of the larger 

 lymph vessels. Frequently these and the mucosa to the height of the 

 fold are closely beset with lymph corpuscles, so much so as to obscure 

 the fibrillar character of the tissues. They frequently are more numer- 

 ous, approximating to patches, but with no definite limit at certain 

 points, at the base of the cylinder cells in the height of a villus. 

 They are probably the analogues of Peyer's glands which appear to 

 be absent in fishes, although the sturgeon has in the mucosa of its 

 spiral valve a number of closed spherical cavities surrounded by a 

 sheath of dense adenoid tissue and filled by a great quantity of 

 corpuscles. These', I would say, are the nearest, probably the only, 

 approach to a likeness of Peyer's glands in fishes. 



The surface of the membrane is increased by deep crypts which 

 are lined with an epithelium like that of the general surface. These 

 crypts are never branched, being simply straight tubules. They 

 represent in fishes the Lieberkuhnian glands of higher vertebrates, 

 although the epithelium constituting them is not differentiated. 



The epithelium consists of long cylinder cells, among which are 

 found modifications of them in the form of beaker cells. The cylin- 

 der cell is of equal diameter in its upper two-thirds, and has a fine 

 basal process running into the tissue of the mucosa. I have never 

 succeeded in isolating it to its fullest extent. As far as it has been 

 separated it was observed to be varicose in its course and frequently 

 branched. The situation of the large oval nucleus is various, and 

 when a section is viewed several layers or stratifications of nuclei 

 are observed. Nucleolar bodies may be present in the nuclei. In 

 the protoplasm of the upper half of the cell are a quantity of 

 granules, fine and coarse, the latter abounding, and after food has 

 been in the midgut for some time, fat globules. These diminish in 

 quantity towards the nucleus. In transverse section these cells 

 .appear hexagonal in outline. The peripheral wall is quite thick, 



