PLATE 15 
EXPLANATION OF FIGURES 
Cleavage stages; all magnifications X 200. 
1 2-celled ovum No. 203 (8), 11th section (total 20); compare figs. E and F, 
text fig. 4; Hill’s fluid; 5 yu. 
2 2-celled ovum No. 306 (1); 9th section (total 23); compare figs. A and B, 
text fig. 4; Hill’s fluid; 5 p. 
3 3-celled ovum No. 173 (8); 10th section (total 21); compare fig. L, text 4; 
aceto-osmic-bichromate; 5 yu. 
4 3-celled ovum No. 306 (3); 11th of 22 sections; compare K, text fig. 4; Hill’s 
fluid; 5 wu. 
5 4-celled ovum No. 293 (2), with two blastomeres in mitosis; drawn from 
clay model; total 18 sections, Bouin; 5 1; compare fig. 1, pl. 2. 
6 4-celled ovum No. 293 (4), with two cells in mitosis; drawn from clay 
model; Bouin; 18 sections; 5 4; compare fig. 1, pl. 2. 
7 4-celled ovum No. 203 (7); 10th section (total 20); see text; Hill’s fluid; 5 yu. 
8 4-celled ovum No. 83 (7); 11th section (total 18); blastomeres cut as in 
* preceding; one polar body; Bouin; 5 wp. 
9 and 10 5th and 9th sections through ovum No. 17’ (7) one of 438 very 
small eggs from one ovary; total 11 sections. 
11 and 12 7th and 14th sections (total 19) through ovum No. 83 (8), with 
portions of shell membrane and albumen; two polar bodies; Bouin; 5 u. 
13 4-celled ovum No. 299 (7), also shown reconstructed in 0, text fig. 4; 9th 
section (total 20); trichloracetic; 5 pu. 
14 4-celled ovum No. 299 (5), of which sections 9 and 14 are shown in figs. 6 
and 7, pl. 3; 13th section (total 22); Hill’s fluid; 5 u. 
15 6-celled ovum No. 85 (5); 7th section (total 16); blastocyst formation 
already anticipated; Bouin. 
16 15-celled ovum No. 337 (1); 8th section (total 19); one-half strength 
Bouin; 5 zu. 
17. 16-celled ovum No. 85 (12); 8th section (total 21) ; blastomeres still rounded; 
one misplaced cell; Hill’s fluid; 5 uw. 
18 17-celled ovum No. 336 (1); 9th section (total 18); Bouin; 5 z. 
19 26-celled ovum No. 336 (2); 11th section (total 17); Bouin; 5 z. 
20 28-celled ovum No. 342 (1); 8th section (total 18); half-strength Bouin; 
45) [te 
