920 PROFESSOR W. C. MSINTOSH AND MR E. E. PRINCE ON 
circular fibres appears. This portion of the alimentary canal lies in a spacious recess in the 
liver, and two lateral hepatic masses abut upon, but do not actually arch over it. In the 
post-larval wrasse a similar relation of the canal and the liver is noted. The prominent 
wrinkles of the gut in Anarrhichas disappear about the region of the pectoral fins, the 
canal forming a rounded thick-walled tube with one or two triangular folds. After passing 
the yolk-sac the canal is larger than in front, and transversely elongated im section, the 
mesenterial band fixing it to the roof of the abdominal cavity, though it is free elsewhere. 
[ts contour is, however, broken superiorly by the wall of the large portal vessel. A com- 
paratively smooth portion of the gut follows, but folds again make their appearance, in 
the form of five or six prominent rugze in section. The mesentery dorsally is thickened, 

and is almost divided into two portions by a constriction—an upper rounded band, and 
which is thinned off superiorly. The rugze now diminish, the mesentery disappears, 

a lower 
and the urinary vesicle takes its place, while the anus opens externally, Proceeding 
backward, the epithelium of the gut is found to become finer and larger ; indeed, in section, 
posteriorly, it resembles that so characteristic of the alimentary wall in the Annelida ; 
then the folds reappear towards the rectum, and show a somewhat radial striation, 
The alimentary canal in the young salmon differs considerably from the foregoing in 
the region just behind the branchize, since it forms a lax tube im transverse section, with 
thin walls greatly flattened from above downward. The wall increases in thickness in 
the region of the pectoral fins, and the circular coat assumes larger dimensions, so that 
the canal is less flattened. It is comparatively small for the size of the fish, the lumen 
being really smaller than that of the aorta. Towards the posterior part of the pectorals 
the gut is even less than in front of them. The epithelial (mucous) layer then begins 
to increase, and a folded condition of the gut causes two layers to appear in transverse 
section, a smaller superior and a larger inferior. In front of the liver the small calibre of 
glandular) layer outside. 
In the hepatic region the lumen of the gut greatly enlarges, though it is still proportionally 
the epithelial coat is in contrast with the thick circular ( 
less than in the wolf-fish. Behind the liver it shghtly diminishes in diameter, and again 
somewhat enlarges, before assuming the rounded condition characteristic of the rectum, 
the calibre of which is also smaller. The folds of the gut are much less prominent than 
in the wolf-fish ; and the inner surface of the large cylindrical cellular layer of the rectum 
is almost smooth. Some of these features, however, may partly be due to the state of the 
preparations. In the newly-hatched and living salmon, again, the alimentary canal appears 
between the yolk-sac and the anus as a greenish band. About the tenth day distinct 
transverse markings are observed in the tract, two especially conspicuous above the origin 
of the ventral fin. Between the fourth and fifth weeks, the functional activity of the 
alimentary canal is considerable, and numerous feecal masses occur in the rectum. The 
teeth are now evident in both upper and lower jaws. A little later food of various kinds 
is found in the stomach and intestine. The pyloric ceca on the nineteenth day form mere 
conical elevations on the duodenum, and have the aspect of short papillz of a cellnlo- 
eranular nature. It is remarkable that the pancreas (assuming the ceeca to represent it) 
ee 
