The first of a series of studies on the comparative histology of the digestive tubes of fishes selected, on the basis of their feeding habits, from the teleost group: a study of the microscopic anatomy of the digestive tube of a predaceous teleost, the sea bass (Centropristes striatus (L.)). Based on studies of sections, with details of gross anatomy from both fresh and preserved material. Includes a short survey of previous work. Deals with the histology of the various regions of the tract, their tunics and tissues, together with details of cell structure and arrangement. Approach is made from the physiological side, with particular reference to the adaptation of histological elements to functional activity. Parts treated in detail are esophagus, cardiac and pyloric limbs of the stomach, intestine, and pyloric caeca. Particular stress is laid on the histological structure and arrangement of the tunica mucosa, especially in relation to digestion and absorption. Topics given particular emphasis are: condition of mucosal folds with reference to the amount of food present in the lumen; transformation between adjacent epithelia of different types; structure of cardiac and pyloric glands; origin and differentiation of intestinal goblet cells; comparisons between histology of pyloric caeca and that of adjacent intestine, together with general conditions found in the caecal mucosa.

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This paper presents the third of a series on comparative microscopic anatomy of the entodermal tract of certain teleost fishes, selected for their feeding habits: A study of the histology of the digestive tube of a bottom‐feeding species, the Carolina sea robin (Prionotus carolinus (L.)). Mainly from study of sections, but dissections of both fresh and preserved material were employed to furnish the necessary background of gross anatomy. A short résumé of the literature is given. Treats the general histology of the different divisions of the tube, the tunics and tissues present, and findings on structure and arrangement of cells. Particular emphasis is placed on histological adaptations to meet the demands of physiological processes. Escphagus, stomach, intestine and pyloric caeca are given detailed treatment. The tunica mucosa, with its histological constituents and their arrangement, receives particular stress, being considered in relation to various phases of digestion and absorption. Particular consideration is given to the following: Effects of amount of food present in the tube on extent of mucosal folding; histological transitions from one region of the tract to another, particularly as regards epithelia; histology of peptic glands in cardiac division of stomach; origin and development of mucosal goblet cells; comparisons between the histology of the pyloric caeca and that of the adjacent intestine from which they arise, together with a detailed account of the histology of the former.

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