62 CARL G. HARTMAN 
proportionate number of embryonic and trophoblastic cells is 
apparent from the few examples given in table 6. 
If a comparison be made between the facts shown in table 6 
and the illustrations referred to therein, it is apparent that the 
increase in the number of cells and the differentiation proceed 
pari passu. In figure 15, plate 16—a longitudinal section 
through ovum No. 344 (11)—the formative area is roughly 
marked out by the position of the entodermal cells and the yolk 
and coagulum surrounding them; there is some thinning out of 
the trophoblastic cells. Ovum No. 344 (14) is slightly more 
advanced. It was cut tangentially to the formative area, to 
which nine of the twenty-two sections belong, the limits of this 
area being determined by the presence in the ninth section of 
TABLE 6 
Number of embryonic and trophoblastic cells number of cells 
IDENTIFICA- = 4! EMBRYONIC |TROPHOBLAS- = . 
Savon | xaos |-ar cata | EXTAGEN | omic | “ax Pree 
344 (11) 164 23 71 70 15, XVI 
344 (14) 193 19 76 98 16, and 17, XVI 
356 (4) 283 42 101 140 6 and 7, XVII 
356 (5) 249 48 126 75 10 and 11, XVII 
the last entodermal cells. The further differentiation between 
the two areas, as seen in litter No. 356, is quite apparent from a 
glance at plate 17. 
In the eggs of litter No. 344, of which I have seven excellent 
preparations, the vesicular structure was quite apparent in the 
living state as well as after fixation, but it was not possible to 
show this in the photographs taken after staining them, since the 
albumen also absorbed considerable stain (fig. 2, pl. 6). Two 
eges were, however, photographed alive in Ringer’s solution 
and are shown in figures 5 and 6, plate 8. The former was taken 
in side view and shows the yolk and coagulum hanging in the 
vesicle like a bunch of grapes; in the sections of the egg taken 
longitudinally the relations were found to be as in life (fig. 7, 
pl. 8). The other eggs shown in figure 6 was photographed 
