244 HIIEL. [VorrLx. 
The walls of the anterior epiphysial vesicle (Fig. 12) are two 
or more cells deep. Some of these cells are oval and some 
are pointed, but the pointed cells are not definitely grouped. 
Salmo, 25 mm. long (160 days old). The Epiphysis.—In 
form the epiphysis of Salmo 25 mm. long (Fig. 14, £) 
resembles that of the adult animal. It differs from the 
condition described in Salmo, 13 mm. long, principally in the 
greater elongation of the proximal portion and in its sharper 
differentiation from the distal portion. The proximal portion 
makes up about one-half the length of the organ. It is 
cylindrical, has a transverse diameter of .03 mm. and lies in 
a position nearly at right angles to the long axis of the body. 
The distal portion is flattened dorso-ventrally, its transverse 
axis measures .25 mm., while its dorso-ventral axis measures 
Ir mm. It is bluntly rounded at its free end and passes 
insensibly into the proximal portion at its attached end. It 
extends cephalad from the distal end of the proximal portion, 
with which it forms an angle of about 110°, so that it is not 
quite parallel with the long axis of the body. The formation 
of the cartilaginous roof of the skull between the distal portion 
of the epiphysis and the epidermis has separated the two by a 
considerable interval. The ventral surface of the cartilage is 
excavated for the reception of “the dorsal ‘surface’ of the 
epiphysis, and the excavation is deepest near its cephalic 
end. 
The dorsal wall of the distal portion, as seen in longitudinal 
section, is marked on its outer surface at regular intervals by 
slight excavations, corresponding to which are projections of 
the inner surface into the central cavity. The whole dorsal 
wall has thus the appearance of having been thrown into 
transverse folds. It is necessary to distinguish these apparent 
folds from the actual folds formed later by the blood-vessels. 
Owing to this peculiarity of the dorsal wall the cavity of the 
distal part is very irregular ; it is flattened dorso-ventrally and 
communicates with the brain cavity below through a narrow 
passage in the proximal part. This passage, just before opening 
into the brain cavity, expands like a funnel, and forms what 
Mihalkovics ('77) has called the recessus infrapinealis. 
