GERMINAL MEMBRANE, 37 
embryo is first formed, the germinal membrane. It represents, 
as is known, a round, white, little disc, somewhat above a line 
in breadth, which lies between the vitelline membrane and the 
yelk-substance. This little disc, in a fresh-laid hen’s egg, con- 
sists of globules, which are of unequal size in different parts of 
the germinal membrane. When examined with the microscope, 
they appear much darker than the yelk-globules, (see plate IT, 
fig. 4.) They le in close contact, so that they flatten against 
one another to an hexagonal form. The boundaries of the dis- 
tinct globules may be clearly distinguished, even when in con- 
nexion. They may also be readily isolated from one another, 
and are then round. They contain many smaller round gra- 
nules of various size, with very dark outlines, which float about 
singly when the globules are burst by pressure. Although these 
granules, in most instances, completely fill the globules, yet some 
globules may be observed where that is not the case, and where 
a portion of the globule is transparent, and free from granules, 
(a 6, of the above figure.) I thought that I distinctly saw a double 
external outline on one of these globules (a), which would be 
evidence of the presence of a cell-membrane. Jn most in- 
stances, however, this is not distinct, and my principal reason 
for concluding that they are cells, is, that it is so extremely 
probable that they are developed to form the indubitable cells 
of the incubated germinal membrane. I have not, however, 
fully investigated this process, and only communicate my ob- 
servations on the point, incomplete as they are. If the unin- 
cubated germinal membrane be folded in such a manner that 
its external surface form a sharp margin, that surface is found 
to be tolerably even, dark, and composed immediately of the 
globules of the germinal membrane already described ; the sur- 
face of the germinal membrane of an egg which has been ex- 
posed to brooding heat for four hours, presents a precisely 
similar appearance. The same membrane, when examined also 
upon its general surface, differs but very slightly in appearance 
from one which has not undergone incubation. The globules 
of which it consists merely appear to have more minutely 
granulous contents. But if a germinal membrane after eight’ 
' It is quite as impossible to define with any certainty a fixed time for a precise 
stage of development of the elementary cells of the germinal membrane, as it is to 
connect the formation of the area pellucida, the embryo, and its separate parts, with 
