502 REIGHARD—MAST. [VoL. XIX. 
come elongated to form canals, all of which end blindly at both 
ends, as far as could be determined. One exceptionally large 
vesicle (Fig. 6, c.) was found situated but a short distance 
from the anterior end of the hypophysis in the median plane, 
near its ventral surface. This vesicle is approximately cylin- 
drical, its length being about ten times as great as its diameter, 
which was found to be about five times as great as the diameter 
of any of the other vesicles. It is formed by a layer of 
columnar cells whose inner ends are hyaline while their outer 
ends are granular. No opening could be found leading either 
into or from this cavity. 
At this stage the hypophysis was found to be well supplied 
with blood by vessels (Figs. 5 and 6, b. v.) which enter both 
along the median dorsal and the median ventral surfaces from 
the posterior end. 
On either side of the median line on the dorsal surface 
near the posterior end, there are depressions into which project 
anteriorly directed ingrowths (Fig. 5, hy.) from the ventral 
wall of the infundibulum. These ingrowths distinguish the 
nervous portion of the hypophysis, which is designated ramus 
hyoideus by Goronowitsch (1883), in Acipenser. They vary 
in number in different individuals, there being sometimes two 
on either side of the median line and sometimes one on one 
side and two on the other. They are composed of neuroglia 
(Haller) similar to that found in the walls of the brain tube 
at this stage. In the middle of each protuberance there is a 
rod-shaped core of nuclei which is surrounded by a layer of 
fibrous neuroglia tissue which is separated from the hypophy- 
sis by a limiting membrane. 
We thus have here indicated a division of the hypophysis 
into two portions homologous with the two portions decribed 
by Haller (1897) and others in other vertebrates. 
SUMMARY OF OBSERVATIONS. 
1. The hypophysis of Amia originates at a much earlier 
stage than described by Dean (1896) as a solid mass of 
cells from the inner layer of the ectoblast between the funda- 
