No. 2.] EPIPHYSIS OF TELEOSTS AND AMIA. 247 
distal portion, are found to pass to the lateral and ventral walls 
of the epiphysis. There can be little doubt that all the fibres 
of this column have their origin (nutritive centers) in nerve- 
cells situated in the distal part of the epiphysis. 
Salmo, § cm. long (one year old). — The epiphysis of Salmo 
of 8 cm. is much larger than the epiphysis of Salmo 25 mm. 
long, but resembles it in both form and position. Its distal 
part is flattened dorso-ventrally, and lies dorsal to the cerebrum 
in a median ventral excavation of the cartilaginous plate (Fig. 
15). The principal difference to be noted from the preceding 
stage concerns the relation of the distal part of the epiphysis 
to the surrounding blood-vessels. In the preceding stage 
there had already been formed over the surface of the epiphysis 
a network of transverse and longitudinal capillaries. In the 
stage in question the vessels of this network no longer lie on 
the surface of the epiphysis, but have sunk beneath it. This 
in-sinking is probably not due to any change in the position of 
the blood vessels, but to an increase in the size of the epiphysis, 
which has forced its walls against the capillary network. The 
result is that the walls of the epiphysis have been forced 
into numerous folds, each of which occupies one of the inter- 
spaces of the network. The vessels on the other hand lie 
sunken between these folds and at a distance from the surface 
of the epiphysis (Fig. 15). These vessels never pass through 
the walls of the epiphysis, nor do they penetrate between its 
cells, but lie between the folds, close against its external 
surface. Many of the radiating bands of nerve-cells, which in 
an earlier stage abutted by their outer ends upon the free 
surface of the epiphysis, have now been carried inward by the 
folding of the walls so that they abut upon blood-vessels 
between the folds. 
The anterior epiphysial vesicle lies posterior to the superior 
commissure between the walls of the thalamencephalon and the 
mesencephalon, and against the left side of the stalk of the 
epiphysis. It is an ovoid, compact mass of cells and is some- 
times very difficult to differentiate from the surrounding struc- 
tures. It is a little larger than the corresponding structure in 
Salmo 25 mm. long, but otherwise has undergone no change. 
