No. 2.] THE HYPOPHYSIS OF A MI A CALVA. 77 



I saw the account of the development of the adhesive organ by 

 Miss Phelps. I at once concluded that I had not only con- 

 firmed her discovery, but had also found wherein Kupffer has 

 probably erred in his interpretation of the structures which he 

 believed to be connected with the development of the hypophy- 

 sis, but which to my mind have an entirely different meaning. 

 The statement by Kupffer, that the cells overladen with yolk 

 going to form the hypophysis are not to be distinguished from 

 the elements of the endoderm, receives its explanation in the 

 fact that they are endoclermal cells growing out from the fore- 

 gut by evagination. The canal which, according to Kupffer, 

 connects the foregut with the dorsal ectoderm is nothing else, 

 in the opinion of the writer, than this median diverticulum 

 from the foregut, or possibly one of the lateral diverticula 

 resulting from it, running up through the adhesive organ to 

 the point of closure of the neuropore. A slightly oblique 

 dorso-ventral section through this region in Amia during the 

 sixth day of development would show strikingly similar 

 appearances to those figured and described by Kupffer in 

 Acipenser. 



As a phylogenetic interpretation of the singular development 

 of the hypophysis in Acipenser, Kupffer holds that we here 

 have traces of the ancestral mouth which opened above the 

 sucking disc and in front of the brain. Its origin from the 

 stomodaeal roof as found in most vertebrates, he claims, is a 

 secondary condition due to a migration downwards from its 

 original position, compelled by the great development of the 

 fore brain in these forms and the concomitant degeneration of 

 the adhesive discs, whose remnants, he thinks, are still to be 

 found in the fold between " Rathke's pocket " and the oral 

 plate. 



This explanation fails to account for its origin in Amia and 

 Lepidosteus, in which the sucking disc is still large and func- 

 tional, and whose fore brain is little different from that found 

 in Acipenser ; and yet in them the hypophysis arises at a point 

 far back of the sucking disc and under the brain. 



It may be considered highly probable that the hypophysis is 



