392 E. A. BAUMGARTNER 
logical collection of the Harvard Medical School.? For the pup 
and adult stages special sections and dissections were made. 
The difficulties in making a dissection of the hypophysis in se- 
lachians have been noted by other investigators. In the present 
work, it was possible only after numerous attempts to obtain 
a dissection showing the ventral lobes connected with the rest 
of the hypophysis. Graphic and wax reconstructions of differ- 
ent embryos and parts of the adult Squalus were made. 
LITERATURE 
1. Embryology 
The literature on the development of the elosmobranch 
hypophysis may properly be divided into two categories, one on 
the embryology and the other on the adult anatomy and his- 
tology of this organ. Although the earlier work on the hypophy- 
sis in elasmobranchs concerned its adult anatomy, probably 
investigators have occupied themselves more with its develop- 
ment. Some, of course, have given attention to both the 
adult anatomy and the*development in the same paper or in 
a series of articles. , 
Miiller (71) confirmed Rathke’s earlier observations that 
the hypophysis is developed from the mouth. In Acanth as 
vulgaris and other selachians he found that it was composed of 
a principal posterior part and a secondary anterior part. He 
described the position and gave measurements of the size of the 
hypophysis and of the thickness of different parts of the wall in 
an Acanthias embryo 30 mm. long. In a 10 em. embryo of 
Mustelus he deseribed the tubular masses forming the hypophysis. 
Balfour (’74) briefly stated that the hypophysis is an out- 
pouching from the mouth. In 1878 he described the hypophysis 
as being somewhat constricted from the mouth by the close of 
* Through the courtesy of the late Dr. Charles 8. Minot I was able to make use 
of the extensive Harvard Embryological Collection and had the privileges of his 
laboratory during the summer of 1914. I also wish to thank Dr. J. S. Kingsley 
and others of the South Harpswell Laboratory for the courtesies of that labora- 
tory for a part of the summer. ; 
