PLATE 10 
EXPLANATION OF FIGURES 
Photomicrographs of bilaminar blastocysts. 
1 and 2 Two eggs of litter No. 193’, photographed unstained in alcohol by 
transmitted light; note light field near center of embryonic area; compare fig. 
GU 22 ew a3 
3 1.15-mm. blastocyst No. 360 (5), stained in Delafie!ld’s haematoxylin, cut 
in two horizontally and photographed in alcohol by transmitted light. = 16. 
4 Egg No. 352’ (10), one of the litter shown in fig. 4, pl. 9; 46th section of 
vesicle (total 92); 29th section of embryonic area (total 54); section is oriented 
with embryonic area to left; Hill’s fluid; 5u. X 100. 
5 Egg No. 299’ (6); one of litter shown in fig. 4, pl. 1; shown in toto in fig. 1, 
pl. 6; 61st section of vesicle (total 120); 41st section of embryonic area (total 81); 
the entoderm has not quite reached the lower pole; Hill’s fluid; 54. X 100. 
6 Section of egg No. 360 (5) shown in surface view in fig. 3; section is ori- 
ented with embryonic area uppermost; a little albumen is left at lower pole; 
55th section of embryonic area (total 121). > 100. 
7 Litter No. 306’; interval 5 days, 20} hours, after beginning of cleavage; 
photographed alive in Ringer’s solution. X 8. 
8 Stereogram of ova No. 360 (7), (8), and (9); photographed in alcohol; 
embryonic area seen in two of the eggs; Zenker.  X 6.3. 
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