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SMITHSONIAN MISCELLANEOUS COLLECTIONS
VOLUME 56 NUMBER 11
 
DEVELOPMENT OF THE DIGESTIVE
CANAL OF THE AMERICAN
ALLIGATOR
 
WITH FIFTEEN PLATES
 
BY
ALBERT M. REESE
Professor of Zoology, West Virginia University
 
Smithsonian symbol
(Publication 1946)
 
CITY OF WASHINGTON
PUBLISHED BY THE SMITHSONIAN INSTITUTION
1910
 
 
 The Lord Baltimore Press
BALTIMORE, MD., U. S. A.
 
 
1
DEVELOPMENT OF THE DIGESTIVE CANAL OF THE AMERICAN ALLIGATOR
By ALBERT M. REESE
Professor of Zoology, West Virginia University
In a previous paper (6) the writer described the general features in thedevelopment of the American Alligator; and in other papers specialfeatures were taken up in more detail.
In the present paper the development of the enteron is described indetail, but the derivatives of the digestive tract (liver, pancreas,lungs, etc.) are mentioned only incidentally; the development of theselatter structures may be described in a later paper.
No detailed description of the histological changes taking placeduring development has been attempted, though a brief description of thehistology is given for each stage discussed.
The material upon which this work was done is the same as that usedfor the preceding researches. It was collected by the author in centralFlorida and southern Georgia by means of a grant from the SmithsonianInstitution, for which assistance acknowledgment is herewith gratefullymade.
Various methods of fixation were employed in preserving the material.In practically all cases the embryos were stained in toto with BoraxCarmine and on the slide with Lyon's Blue. Transverse, sagittal, andhorizontal sections were cut, their thickness varying from five tothirty microns, depending upon the size of the embryos.
The first indication of the formation of the enteron is seen in thevery early embryo shown, from the dorsal aspect, in figure 1. The medullary folds and notochord are evidentat this stage, but no mesoblastic somites are to be seen.
A sagittal section of approximately this stage, shown in figure 1A, represents theforegut, fg, as a shallow enclosure of the anterior region of theentoderm, while the wide blastopore, blp, connects the region ofthe hindgut with the exterior. No sign of a tail fold being present,there is, of course, no real hindgut. The entoderm, which has theappearance of being thickened because of the fact that the notochord hasnot yet completely separated from it, is c                        
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