PLATE 19 
EXPLANATION OF FIGURES 
Partially completed and just completed bilaminar blastocysts. 
1 Longitudinal section through ovum No. 205 (4); 41st section (total 93); 
Bowing 0) 
2 Surface view of trophoblastic area of an egg from the litter No. 205; ento- 
derm shaded; ectodermal nuclei unshaded. > 500. 
3 Detail of embryonic area of blastocyst No. 347 (4), shown in fig. 7, pl. 18. 
x 500. 
4 Detail of section through embryonic area of ovum No. 352’ (10), shown 
in’ fie. A pl. 10-5500: 
5and 5A Entire section, 50, and vesicle only, 200, through the middle 
of ovum No. 339 (4), photographed in toto in fig. 2, pl. 6; note swollen cells; 
Bouin; 5 wp. 
6 Embryonic area only of similar egg No. 339 (2); Bouin; 5 4. X 200. 
7 Blastocyst No. 175’ (9), with very attenuated, mostly unilaminar wall; 
52nd section through vesicle (total 89); aceto-osmic-bichromate (?);5 4. X 50. 
7a Embyronic area only of same egg. X 200. 
Sand 8A_ Entire section, X 50, and embryonic area (XX), X 200, of ovum 
No. 347 (5); entoderm has not yet reached equator; 30th section of vesicle (total 
119) and 18th section through area (total 29); Flemming; 5 yu. 
9 The embryonic area of ovum No. 205 (6); 49th section of blastocyst (total 
79); Bouin; 5 uw; compare fig. 1. 
10 Just completed bilaminar blastocyst No. 208 (1); 56th section through 
vesicle (total 117); Bouin.  X 50. 
10A and 10B_ Details of embryonic area and trophoblastic area of same egg. 
xX 200. 
11 Portion of surface view of ovum No. 205 (7); XX, junctional line; only the 
entorderm is shaded; ectodermal nuclei unshaded circles. 500. 
12 Surface view at junctional line (XX) of ovum No. 205 (9); entire ecto- 
derm shaded; embryonic nuclei very dark, trophoblastic nuclei very light; 
entodermal nuclei intermediate in tone. 
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