PLATE 20 
EXPLANATION OF FIGURES 
Completed bilaminar blastocyst. 
1 Section of embryonic area (XX) of blastocyst No. 82 (13), nearly like 
fig. 1, pl. 21; 54th section of egg (total 100) and 38th section of embryonic area 
(total 58); Bouin. X 200. 
1A Detail of same. X 500. 
2 Blastocyst No. 306’ (2) shown in fig. 17, pl. 13; 0.77 mm. in diameter in 
alcohol; 18th section of embryonic area (total 49) and 63d through vesicle (total 
118); compare fig. 7, pl. 10; Hill’s fluid; 54. X 200. 
2A Detail of same near junctional line (X). X 500. 
3 Ovum No. 285’ (1); 72nd section through blastocyst (total 107); Bouin; 
5 uw; the portion of vesicle marked by dotted line was dissected off before in- 
bedding and was stained and mounted in toto (fig. 3B). X 50. 
3A Same blastocyst. X 200. 
3B Surface view from point A, fig. 3; junctional line XX; ectoderm lightly 
shaded; entodermal nuclei darkly shaded. 500. 
4. The 92nd section (total 140) through blastocyst No. 48 (10); two de- 
generating cells at A; Hill’s fluid. X 50. 
44 The embryonic area (XX) of same. X 200. 
136 
