300 G. CARL HUBER 
such an early differentiation of ectoderm and entoderm as given 
by Selenka, Duval, Christiani, and others. Cells of irregular 
outline with tongue-like projections, such as figured by Selenka 
and Duval I have not observed. The cells constituting the 
floor or the thick part of the vesicle all present essentially the 
same structure, while the segmentation cavity, as soon as it 
presents appreciable size, shows a smooth and regular outline. 
In figures 1 and 2, of Widakowich’s communication, excellent 
figures of early stages of blastodermic vesicles of the albino rat, 
there is presented no evidence of a trophoblast layer nor a dif- 
ferentiation of ectodermal and entodermal cells. My own 
figures, 20 to 22, were drawn with the aid of camera lucida at a 
magnification of 1000 diameters and with the use of an intense 
Welsbach light. They are reduced five times in reproduction. 
With the exceptions of cell outlines, which as sketched do not 
in the preparations fall in the same optical plane, and aresketched 
more sharply than is perhaps warranted, the figures portray 
quite accurately the structural appearances presented, so far 
as may be with the use of a single color. 
BLASTODERMIC VESICLE, BLASTOCYST, OR GERMINAL VESICLE 
The material on hand is listed in table 6. 
TABLE 6 
RECORD NUMBER AGE NUMBER OF VESICLES 
75 5 days, 15 hours 6 
91 5 days, 16 hours 2 
88 5 days, 21 hours Sant 
89 5 days, 21 hours 6 
73 6 days 10 
74 | 6 days 5 
99 6 days 6 
106 6 days 10 
104 6 days 6 Total 58 
During the sixth day, the blastodermic vesicle of the albino rat 
increases In size relatively rapidly. The greater portion of its wall 
is, at this stage, composed of a single layer of flattened cells. The 
vesicles are not as yet attached to the uterine wall, though the uter- 
