624 EXPLANATION 
Fig. 20. Ovarian egg, natural size ; fig. 20a, its yolk, 500 
diam. Ch. picta. 
Fig. 21. Ovarian egg, natural size; fig. 21a, its yolk, 500 
diam. Ch. picta. 
Fig. 22. Ovarian egg; a, natural size; 0, the finer yolk, 
500 diam.; c, one of the large yolk cells, 500 diam.; d, 
the same, 1100 diam.; e, Purkinjean vesicle, 500 diam. 
Ch. picta. 
Fig. 28. Ovarian egg, natural size ; fig. 23a, granular yolk, 
500 diam. ; fig. 23b, a, yolk cell, 500 diam.; b, the same, 
1100 diam. ; fig. 23c, a, yolk cell, 500 diam. ; 6, the same, 
1100 diam.; fig. 23d, yolk cells, 500 diam.; a, b, angu- 
lar mesoblasts. Ch. picta. 
Fig. 24. Egg, natural size; fig. 24a, granular yolk, 500 
diam. ; fig. 24b, the Purkinjean vesicle, 500 diam. ; a, a, 
altered mesoblasts. Nanemys guttata. 
Fig. 25. Egg, natural size; a, b, c, d, e, its yolk cells, 500 
diam. Ch. picta. 
PLATE IX. 
[From nature, by H. J. Clark.} 
Fig. 1. Ovarian egg, natural size; fig. 1a, the same, 25 
diam.; a, zona pellucida; 6, Purkinjean vesicle. Ch. 
picta. 
Fig. 2. Egg, natural size ; fig. 2a, a, b, c, d, yolk cells, 500 
diam. Ch. picta. 
Fig. 8. Ege, natural size ; fig. 3a, a, b, c, d, e, g, yolk cells, 
500 diam. Ch. picta. 
Fig. 4. Egg, nat. size; fig. 4a, its Purkinjean vesicle, 500 
diam. ; fig. 4b, the same as fig. 4a, burst open by water, 
500 diam. Nanemys guttata. 
Fig. 5. Egg, nat. size; fig. 5a, Purkinjean vesicle, 40 diam. ; 
fig. 5b, another view of the same as fig. 5a; fig. 5c, the 
same as fig. 5a, and fig. 5b, 500 diam.; a, its granular 
contents ; 6, yolk granules. 
Fig. 6. Egg, nat. size; fig. 6a, a to r, yolk cells, 500 diam. ; 
fig. 6b, yolk cells, near the Purkinjean vesicle, 500 diam. 
Ch. picta. 
Fig. 7. Egg, nat. size; fig. 7a, Purkinjean vesicle, 40 diam. ; 
fig. 7b, contents of the vesicle, 500 diam. ; fig. 7c, 7d, 7e, 
7f, 7g, yolk cells acted upon by water, 500 diam. Ch. 
Fig. 8. Egg, nat. size; fig. 8a, A to N, yolk cells; J, K, 
0D) 
K’, L, L’, 1100 diam., the others, 500 diam. In all the 


1 Some of the yolk granules which surround this Purkinjean 
vesicle are drawn upon its edge, between the outline and fig. 5. 
OF THE PLATES. 


figures, a is the ectoblast, ) the mesoblast, ¢ the ento- 
blast. Ch. picta. 
Fig. 9. Egg, nat. size ; fig. 9a, Purkinjean vesicle, 40 diam. ; 
fig. 9b, another view of the same; fig. 9c, the same as 
fig. 9a, 500 diam. ;* a, b, granular contents. Ch. picta. 
Fig. 10. Egg, nat. size; fig. 10a, Purkinjean vesicle, 40 
diam. ; fig. 10b, another view of fig. 10a; fig. 10c, the 
same as fig. 10a; a, b, granular contents, 500 diam. Ch. 
picta. 
Fig. 11. Egg, nat. size; fig. 11a, Purkinjean vesicle, 40 
diam. ; fig. 11b, the same as fig. 1la, 500 diam.; a, 6, 
its granular contents; fig. 11¢e, yolk cells around the 
Purkinjean vesicle, 500 diam.; fig. 11d, the same as 
fig. 11¢e; fig. 11e, yolk cells, 4g of an inch below the Pur- 
kinjean vesicle, 500 diam.; fig. 11f, yolk cells, } of an 
inch below the Purkinjean vesicle; fig. 11g, yolk cells, 
from the centre of the egg, 500 diam.; fig. 11f, yolk cells 
pressing against each other, 500 diam Ch. picta. 
Fig. 12, a, b, c, e, f; mesoblasts, altered by water, of yolk 
cells of an egg from the oviduct that had its shell; d, d’, 
pieces of the walls of the mesoblast. Ch. picta. 
PLATE Xa. 
[Fig. 82, 82a, from nature, by A. Sonrel, the others by H. J. Clark.] 
Fig. 1. Yolk cells from an egg in the oviduct, 500 diam. 
Chrysemys picta. 
Fig. 2, 2a, 2d. 
June 12, opened June 26, 1852. Nanemys guttata. 
Yolk cells, 500 diam., from an ege laid 
Fig. 3. Yolk cells from the germinal layer, 500 diam. Egg 
laid June 15, opened June 16, 1854. Chelydra serpen- 
tina. 
Fig. 4. Yolk cells from the germinal layer. See fig. 2, 2a, 
2d, for their age. 
Fig. 5. Heaps of mesoblasts in the germinal layer, 250 
diam. ; fig. 5a, one of these heaps, 500 diam. For age, 
see fig. 2, etc. 
2 One half only of this Purkinjean vesicle is drawn; its outline 
passes by fig. 9c, and its contents are represented on the right side, 
along the frame of the Plate. 
3 Here also the outline of one half only of the vesicle is drawn, 
passing by fig. 10c, and the contents on the right along the frame of 
the Plate. 
4 The yolk cells, fig. 11d to 11h, scattered over the Purkinjean 
vesicle, fig. 11b, in order to save room, are, of course, out of place 
there, but those on its edge, fig. 11c, are in place. 
5 This, and similar references to other figures, are intended to 
point out the connection between the different objects represented. 

