No. 2.] EPIPHYSIS OF TELEOSTS AND AMIA. 253 
brain-roof, and in a left profile view appears to lie between the 
latter and the anterior border of the posterior vesicle. 
I have made no sections of Catostomus, Stizostedion, and 
Lepomis, but have worked exclusively on living forms. 
AMIA. 
In Amia calva there are two epiphysial vesicles, just as in 
Salmo and the other Teleosts described. These vesicles arise 
from a common median point in the posterior part of the 
primary fore-brain between the posterior and superior com- 
missures. I have studied their development in Amia 10 mm. 
long to Amia 15 mm. long, but owing to lack of material I 
am unable to describe their earliest condition, or to give their 
subsequent history. My study of Amia is confined to sections. 
The posterior epiphysial vesicle or epiphysis, in Amia 10 mm. 
long, is an obovoid body which tapers a little towards its distal 
end. It is attached by a narrow short stalk to the roof of the 
thalamencephalon in the median plane and between the poste- 
rior and the superior commissure (Fig 22). Its middle point lies 
a little to the right of the median plane, while its distal end is 
turned caudad and lies dorsal to the posterior commissure. Its 
dorsal surface is convex and lies close against the integument, 
while its ventral surface is plane and is applied to the brain- 
wall. This vesicle contains a narrow cavity which extends 
nearly to the distal end and which communicates with the 
brain cavity below. This cavity separates a thick ventral 
wall, three or four cells deep, from a thin dorsal wall of 
but a single layer of cells. The boundaries of the cavity 
are sharply contoured only where it opens into the thala- 
mocoel, and here they diverge to inclose the funnel-shaped 
recessus infrapinealis. . 
In Amia 13 mm. long the formation of a fold has carried 
the posterior commissure ventrally into the thalamocoel and 
the epiphysis has assumed a nearly vertical position. It lies 
close against the integument with its distal end some distance 
removed from the posterior commissure. In Amia 15 mm. long 
this separation of the epiphysis from the posterior commissure 
