Se G. CARL HUBER 
Vesicle C of figure 24 (rat No. 54, 6 days, 16 hours) presents a 
stage which is almost identical in development with that shown 
in B of this figure, though in shape these two vesicles, as seen in 
sections, appear quite different. The vesicle shown in C is less 
compressed than the one shown in B, and probably presents more 
correctly the form of the blastodermic vesicle or blastocyst of 
the albino rat at this stage of development. The ectoplacental 
cone presents a cylindrical outline and contains two cells showing 
mitotic phases, both included in the section figured. Its cells, 
more particularly the ones bordering the periphery, present a 
vacuolated protoplasm, the vacuoles containing lightly colored 
globules which from reaction to the stain are to be regarded as 
blood cells or fragments of such, which blood cells are regarded 
as of maternal origin. In this preparation, the decidual crypt 
contains a small amount of extravasated maternal blood, found 
in part surrounding the ectoplacental cone; also in the antimes- 
ometrial portion of the crypt in relation with the roof of this 
vesicle. These findings will receive further consideration in the 
succeeding pages. The cell mass projecting into the cavity of 
the vesicle, consisting of the ectodermal node and the layer of 
visceral entoderm is slightly larger than in the preceding stage 
but presents no special features deserving discussion. The vesi- 
cle in the section sketched presents very few cells of the parietal 
entoderm. The parietal ectoderm forming the roof of this 
vesicle consists of a single layer of flattened cells in the proto- 
plasm of certain of which vacuolization is evident. Certain of 
. the cells show inclusions of lightly staining globules of a color 
similar to those found in the cells of the ectoplacenta, particularly 
evident in the lower right of the figure in which they are repre- 
sented as uncolored circumscribed areas. The color reaction 
of these globules is like that of the maternal blood cells and frag- 
ments of blood cells found in the decidual crypt in the immediate 
vicinity of the vesicle, and they are regarded as blood cells or 
fragments of such, taken up by the cells of the parietal ectoderm 
at this stage in the development of the vesicle. 
The blastodermic vesicles or blastocysts figured in figure 24, 
represent an important stage in the development of the albino 
