No. 2.] EPIPHYSIS OF TELEOSTS AND AMIA. 245 
The anterior cpiphysial vesicle has the position, form and 
histological structure described for the anterior vesicle of Salmo 
13 mm. long (Fig. 9, Z’). Usually a longitudinal section of 
the brain through this vesicle passes also through the distal 
portion of the epiphysis a little to the left of the median plane. 
The walls of the anterior vesicle have fused, and the vesicle is 
thus reduced to a solid mass of cells, wedged in between the 
thalamencephalon and mesencephalon, and entirely without 
connection with any surrounding structure. 
The integument dorsal to the epiphysis consists of two 
layers of flattened cells. The cells of the outer layer are 
parallel to the surface, while those of the inner layer are placed 
obliquely. Between this integument and the cartilage is a 
compact layer of tissue which becomes the frontal bones of 
the adult. 
The apparently elevated area of the roof of the thalamen- 
cephalon, which lies immediately in front of the epiphysis, has 
its lateral portions thrown into secondary folds (Fig. 9). These 
folds project into the thalamocoele, and other similar folds 
appear in the roof of the thalamencephalon at the sides of the 
epiphysis. The epiphysis is thus walled in by these folds 
laterally, by the elevated area of the roof of the thalamen- 
cephalon cephalad and by the mid-brain caudad, so that it 
appears to lie in a median longitudinal depression of the brain 
roof. 
Fibre tracts and nerve-cells are well developed throughout 
the brain. This is especially true of the anterior portion of 
the mesencephalon. 
Histology.—— The cell structure of the proximal part or stalk 
of the epiphysis is essentially the same as that described in the 
epiphysial stalk of Salmo 13 mm. long. In the distal end of 
the epiphysis the cells are all oval and have no regular arrange- 
ment, while in the rest of the distal portion, and especially in 
the dorsal wall, most of the cells are pear-shaped. In a 
horizontal section through the dorsal wall these cells are seen 
to be arranged in transverse bands (Fig. 13). Each band 
presents in section two rows of cells separated by a narrow, 
deeply stained line. This line has a fibrous structure and is 
