58 P RATHER. [VOL. I. 



Rathke ('38), Luschke ('60), Kolliker ('61), Miklucho-Maclay 

 ('70), W. Miiller ('71), His ('75), Hatschek ('81), Dohrn ('81), 

 Owen ('82), Balfour and Parker ('82). 



It should be emphasized that, in general, this was claimed 

 for the particular form investigated, but not claimed to hold 

 true for all vertebrates. 



2. That the hypophysis is of epiblastic origin, as claimed by 

 Goette ('72), Balfour ('74), Mihalkovics ('74), Kolliker ('76), 

 Cattie ('81), Julin ('81), Dohrn ('82), Kraushaar ('83), Johnson 

 and Sheldon ('86), Orr ('87), Scott ('87), Kupffer ('90), Lund- 

 borg ('94), Dean ('96), Haller ('96), Braem (98), Minot ('98). 



It should be added that the majority of these observers not 

 only claimed the hypophysis to be of epiblastic origin in the 

 particular form examined, but also believed this to hold good 

 for the Vertebrata. 



3. That the hypophysis is partially of hypoblastic and partially 

 of epiblastic origin, as positively maintained by Kupffer ('93), 

 Valenti ('95), and Nussbaum ('96), and considered probable by 

 Hoffmann ('85), Orr ('87), and Gaupp ('93). 



The researches made by the above-named writers show that 

 the organ varies so much in its development and structure in 

 the different forms that generalizations should be made with 

 extreme caution, until more extended and precise observations 

 have been made. 



While its development has been more or less carefully traced 

 in animals representing nearly every group of vertebrates, I 

 find that the Ganoids have received but little attention. Kupffer 

 has described and figured its earliest stages in Acipcnser sturio. 

 This author finds such an unusual mode of development that it 

 seems possible that he has misinterpreted certain structures 

 connected with the development of the sucking discs, for, as 

 the sequel will show, at a certain stage in their formation in 

 Amia these discs present appearances very similar to those 

 regarded by him as the beginnings of the hypophysis. A 

 fuller discussion is reserved for a later page. 



Balfour and Parker have figured some of its early stages 

 in Lcpidostcns osscus, but have given no adequate descrip- 

 tion of its origin. Judging from their figures and few 



