No. 2.] EPIPHYVSIS OF TELEOSTS AND AMTA. 249 
surface, the folds present in the preceding stage have deepened, 
and from them secondary folds have been formed. They have 
increased in number, depth and complexity, and involve nearly 
the whole distal part of the epiphysis. The cavity of the 
epiphysis extends into both primary and secondary folds. In 
individual sections those portions of the central cavity which 
extend into the folds often appear to be independent of the 
central cavity and widely separated from it, but in series of 
sections it is always possible to trace a connection between 
the two. Between nearly all the folds are to be found blood- 
vessels which frequently lie far from the surface, but, just as 
in Salmo one year old, they never lie between its cells. On 
the contrary, they are always removed from the cavity of the 
epiphysis a distance equal to the thickness of its walls. 
Anterior epiphystal vesicle. — The anterior epiphysial vesicle 
is present as a small mass of cells occupying the same position 
as that described in younger forms. I have found it in only 
one individual of this age, and in this its size was about two- 
thirds that of the anterior epiphysial vesicle of the yearling 
fish. Its structure was unchanged. 
Ffistology. — It is convenient to distinguish four regions in 
the epiphysis at this stage. These are: 1. The distal one- 
fourth of the distal portion of the epiphysis. 2. The remainder 
of the distal portion. 3. The distal part of the stalk. 4. The 
proximal end of the stalk. The regions pass into one another 
by insensible gradations but differ in their histological char- 
acters. 
The first region has retained its embryonic structure. The 
wall is here made up of about two layers of round cells 
uniformly distributed in a granular matrix, and is neither 
folded nor penetrated by blood-vessels. 
The second region. — As one passes from the first part of the 
epiphysis toward the stalk the folds of the wall and their 
accompanying blood-vessels gradually make their appearance 
and increase in depth and complexity to about the middle of 
the length of the distal portion. The folds then become again 
less pronounced and finally disappear at the distal end of the 
stalk. In this part of the distal portion are found the bands 
