GERMINAL MEMBRANE. 57 



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 lien'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 II, 

 fig. 4.) They lie 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 b, of the above figure.) I thought that I distinctly saw a double 

 external outline on one of these globules («), which would be 

 evidence of the presence of a cell-membrane. In 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 1 



1 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 



