1902 - 3 .] Mr John Cameron on the Pineal Body. 573 
examination of other specimens in order to determine whether 
the above condition was a normal one, or whether it was merely 
an anomaly. 
For this purpose transverse sections of tadpoles of the frog 
(Rana temyoraria) and toad ( Bufo vulgaris ), as representing the 
Anura group of Amphibia; and tadpoles of the newt (Triton — 
species V), as representing the TJrodela group, were prepared. A 
total of thirty-seven embryos were examined in this way. In 
most of the specimens of the earlier stages, which were investi- 
gated, it was found that the opening of the epiphysis lay dis- 
tinctly to one side of the middle line. 
At the same time it was easy to demonstrate the fact that the 
opening lay to the left of the middle line in those instances where 
it was amesial in position. On examining the very earliest stages 
of development of the epiphysis, however, an interesting condi- 
tion of matters was made manifest ; for, sections of a frog-embryo 
4 mm. long (ten days after fertilisation ; previous to hatching) 
showed the presence of two small recesses from the roof of the 
fore-brain, placed immediately on each side of the middle line, and 
separated from one another by a narrow vertical process (fig. 1). 
On examining this figure it will be observed that the right recess 
is somewhat the larger of the two. Each recess will also be 
observed to be lined with a layer of pigment. This corresponds 
to the pigmentary layer which de Graaf has described as lining 
the epiphysial evagination in Bufo cinerea. However, instead of 
a single evagination such as de Graaf describes, there are really 
two small lateral recesses present at this early stage, and the whole 
structure is to be looked upon as being bilateral, and not mesial in 
origin. 
The roof of the fore-brain in such young frog-embryos is 
composed of several layers of cells, so that the epiphysial rudi- 
ments do not at once give rise to distinct evaginations, but appear 
as simple recesses from the brain-cavity. The wall of the cerebral 
vesicles is loaded with yolk granules during these early periods of 
development, and they are apt to obscure its structure ; but they 
are not represented in the figure, as this would have proved too 
confusing. The presence of the pigment also increases the diffi- 
culty of deciphering the structure of the cerebral wall, and, indeed, 
