author's abstract of this paper issued by 

 the bibliographic service, november 7 



THE DEVELOPMENT OF THE PHARYNX AND AORTIC 

 ARCHES OF THE TURTLE, WITH A NOTE ON THE 

 FIFTH AND PULMONARY ARCHES OF MAMMALS 



. RALPH FAUST SHANER 

 Harvard Medical School, Boston, Massachusetts 



FOUR PLATES (FIFTEEN FIGURES) 



Although there have been several studies of the development 

 of the reptilian pharynx, few of them have been made with the 

 aid of wax models and the other more exact methods so often 

 used in researches on mammals. This communication em- 

 bodies the results of an application of such methods to the 

 most available American reptiles, the common fresh-water 

 painted turtles, Chrysemys marginata and C. picta. Atten- 

 tion has been directed chiefly to the third, fourth, and fifth 

 pouches and the postbranchial body. It seemed worth while 

 to include also a study of the aortic arches. Of the many papers 

 on these vessels, few treat of the relations of the arches to the 

 pharynx. A study of the vessels in connection with the pharynx 

 brings some new facts to light which have a bearing on the 

 nature of the fifth and pulmonary arches of mammals.^ For 

 the drawings of the models I am indebted to Mr. H. F. Aitken, 

 who has represented these difficult objects with skillful fidelity. 



In the turtle, as in reptiles generally, there develop five pouches, 

 exclusive of the postbranchial body. The first four are ordinary 

 lateral outgrowths of the entoderm (figs. 1 to 4). The thin 

 membrane that bars communication between the pouch and 

 the exterior is broken through in the first three pouches; 

 the fourth, in all likelihood, is always closed. Each pouch is 

 furnished with a branchial placode. In younger embryos — up 



^ A preliminary report of these observations was presented at the meeting of 

 the American Association of Anatomists in Philadelphia, 1921. See Proceedings, 

 Anat. Rec, vol. 21. 



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