THE EARLY DEVELOPMENT OK THE 

 HYPOPHYSIS IN CHELONIA. 



s ZKI.KNY. 



THE following observations on the early development of the 

 hypophysis in Chelonia are offered at this time because they 

 throw positive light upon the derivation of the organ concern- 

 ing which we at present have several conflicting views. The 

 paper is based upon sections of Aspidonectes spinifer Ag., 

 Chelydra serpentina L., and Chrysemys marginata Ag., which 

 show that in these forms the hypophysis is undoubtedly of 

 epiblastic origin. Incidentally some points regarding the rela- 

 tion of the preoral gut to the notochord and the head cavities 

 will be noted, but this subject will receive fuller treatment in a 

 subsequent paper. Kor the sake of convenience the subject 

 matter will be considered under the following heads : 



1. A general outline of the literature dealing with the early 

 development of the hypophysis among vertebrates. 



2. Material and methods of preparation. 



3. Description of stages. 



4. Summary and conclusion. 



Literature. 



It would be out of place in a paper such as the present 

 to give any detailed account of the views which have been 

 held regarding the subject under discussion. A bare mention 

 of a few of the upholders of each of the principal views, giving 

 the group upon which work was done, must suffice. 



i. Those who have claimed a hypoblastic origin for the 

 hypophysis are Luschka ('69), Mammalia ; W. Miiller ('71), 

 Vertebrata in general ; Dohrn ('82), Teleostii, later extended to 

 Vertebrata in general ; Hoffmann ('8), Lacerta ; Prather ('99), 



Amia. 



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