No. 2.] EPIPHYSIS OF TELEOSTS AND AMIA. 239 
Satmo.! 
Salmo 7 mm. long. — In Salmonidae, as in all other verte- 
brates, the epiphysis has its origin in the roof of the primary 
fore-brain just cephalad of the posterior commissure. Two 
small dorsal evaginations of this brain-roof may be found in 
the embryos of all the species of Salmo that I have studied. 
In Coregonus albus I ('91) have designated them as the poste- 
rior and the anterior epiphysial vesicles, and I shall use the 
same words for the corresponding structures of Salmo. 
Posterior epiphysial vesicle. — In Salmo 7 mm. long, the 
posterior epiphysial vesicle (Figs. 1, 2, 3 and 4, £) is a small, 
nearly globular evagination in the posterior part of the roof of 
the primary fore-brain. In its center there is a cavity, the 
middle of which lies a trifle to the right of the median line of 
the brain so that the vesicle is turned a little to the right. 
This cavity has the form of a compressed funnel with concave 
lateral surfaces, and opens ventrally by its narrower end into 
a short passage which is common to it and the cavity of the 
anterior epiphysial vesicle. The lateral walls of the vesicle are 
biconvex. In their thickest middle portion they are about 
twice as thick as the dorsal wall at its middle. The dorsal 
wall is also biconvex and its outer surface has a lesser radius 
of curvature than its inner surface. The vesicle is thinnest at 
the junction of its dorsal and lateral walls. 
Anterior epiphystal vesicle. — The anterior epiphysial vesicle 
is a club-shaped or ob-ovoid body (Figs. I, 2, 3 and 4, £’). It 
lies to the left of the median plane of the brain and close 
against the posterior vesicle. Its bulk may be estimated at 
two-thirds that of the anterior vesicle. Its distal end is bent 
slightly caudad, and its long axis is directed laterad and dorsad 
so as to form with the dorso-ventral diameter of the posterior 
vesicle an angle of about 75 degrees. It lies in such a position 
that in a profile view its anterior border coincides with that 
of the posterior vesicle. Along its middle there is a narrow 
cavity which curves in conformity with the anterior border of 
1 Salmo fontinalis Mitch. S. purpuratus, Pallas, and S. fario L. 
