EXPLANATION OF THE PLATES. 
Fig. 6. Heaps of mesoblasts, lower side of embryonic dise, 
250 diam. 
Fig. 7. Yolk cells from the lower side of the embryonic 
dise ; a, b, mesoblasts ; fig. 7a, the same as fig. 7, burst by 
For age, see fig. 2. 
water; 500 diam. From the oviduct. 
Fig. 8. Mesoblasts on the upper surface of the embryonic 
dise, 500 diam. For age, see fig. 2. 
Fig. 9, a,b. Yolk cells from the lower surface of the embry- 
onie disc; a’, the mesoblast, acted upon by water; 500 
diam.; a/!, the same asa/, 1100 diam. From the oviduct. 
Chrysemys picta. 
Fig. 10, and 11. Graafian follicles, 500 diam. Ch. picta. 
Fig. 12. Ovarian egg, nat. size; fig. 12a, cells of the zona 
pellucida; 500 diam.; fig. 12b, cells of the tunica gran- 
ulosa, 800 diam. Ch. picta. 
Fig. 13. Piece of the Graafian follicle (see Pl. 8, fig. 12) ; 
fig. 13a, surface view of the polygonal cells of the tunica 
granulosa ; 300 diam. 
Fig. 14. 
the Graafian follicle ; fig. 14a, tunica, surface view; 500 
Ch. picta. 
Piece of the tunica granulosa, and stroma (a) of 
diam. 
Fig. 15. Embryonal membrane from an ovarian egg (see 
fig. 16). 
Fig. 16. 
pears like a black dot. Fig. 16a, portion of the Graafian 
Ovarian egg, 
nat. size ; the Purkinjean vesicle ap- 
follicle around fig. 16; a, stroma; }, tunica granulosa; 
c,zona pellucida; d, yolk; 500 diam. Chrysemys picta, 
and Nanemys guttata. 
Fig. 17. Portion of Graafian follicle inclosing an egg; a, 
the yolk; b, zona pellucida; c, tunica granulosa; d, 
stroma; 500 diam. Ch. picta, and N. guttata. 
Fig. 18. 
Graafian follicle; a, stroma; 0, tunica granulosa; c, vitel- 
Ovarian ege. 
ee, nat. size; fig. 18a, portion of the 
line sac; d, yolk; e, zona pellucida; 500 diam. Ch. 
picta. 
Fig. 19. Piece of the zona pellucida, 500 diam. From an 
ovarian egg (see fig. 20). Ch. picta. 
Fig. 20. Ovarian egg, nat. size; fig. 20a, a, b, embryonal 
membrane, 500 diam. Ch. picta. 
Fig. 21. 
membrane, 500 diam. Glyptemys insculpta. 
Ovarian egg. 
ge, nat. size; fig. 2la, its embryonal 
Fig. 22, and 22a. Embryonal membrane from a full-grown 
ovarian egg, 
Fig. 23. 
8. Chelydra serpentina. 
500 diam. Chrysemys picta. 
Embryonal membrane. For age, see Pl. 11, fig. 
Fig. 24. Embryonal membrane, 500 diam.; fig. 24a, the 
same as fiz. 24,1100 diam. For age, see Pl. 11, fig. 1. 
Chrysemys picta. 
Fig. 25. Embryonal membrane, 500 diam. For age, see 
Pl. 11, fig. 2. Ch. picta. 
79 


625 
Fig. 26. 
duct. 
Fig. 27. 
been laid about 18 days. 
Fig. 28. 
Fig. 29. _Embryonal membrane, surface view ; fig. 29a, pro- 
From the ovi- 
Ch. picta. 
Embryonal membrane, 500 diam.; the egg had 
Embryonal membrane, 500 diam. 
For age, see Pl. 11, fig. 2. 
Amnios, 500 diam. For age, see Pl. 12, fig. 6. 
file; a, yolk; b, cells of the embryonal membrane; 500 
diam. Chelydra serpentina. For age, see fig. 25, and 
Pl. 11, fig. 2. 
Fig. 30. The allantois, inner surface; fig. 30a, outer sur- 
face ; a, cells of the inner surface; 500 diam. Chelydra 
For age, see Pl. 15, fig. 1, 2, 3. 
Fig. 31. The embryonal membrane, (a,) the amnios, (6,) 
serpentina. 
and the allantois (c) of an egg from which the young 
turtle is about hatching; fig. 31a, a single cell of each 
of these membranes; view from the outside of the egg; 
500 diam. Chelydra serpentina. 
Oct. 25, 1855. 
Fig 32. A full-grown ovarian egg of Cistudo virginea, 3 
Laid June 21, opened 
diam. ; to show the convergence of the bloodvessels 
around a central area and the Purkinjean vesicle on 
the left of it; fig. 32a, the Purkinjean vesicle as seen at 
the surface of the mature egg, 5 diam. 
Fig 33. Yolk cell, and its segmenting mesoblast; fig. 33a, 
yolk cell almost filled by its mesoblast; fig. 33b, yolk 
cell filled by its mesoblast; 500 diam. From the oviduct ; 
Aug. 7, 1856. 
Fig. 34. 
side; 500 diam. Chelydra serpentina. For age, see Pl. 
11, fig. 3. 
Fig. 35. 
layer; 500 diam. From the oviduct; the egg had just 
Cinosternum pennsylvanicum. 
Germinal layer; a, the outer surface; b, under- 
An alcoholic preparation. 
Surface of the embryonic area; fig. 35a, germinal 
commenced to segment; see Pl. 10, fig. 1, and 2; an alco- 
holic preparation. Glyptemys insculpta. 
Fig. 36, 36a, 36b, 36c. Yolk cells from close beneath the 
segmenting embryonic area (see Pl. 10, fig. 1, and 2). 
Fig. 37, 37a, 87b, 37e, 37d, yolk cells from the side of the 
same egg; 500 diam.; from the oviduct. Glyptemys in- 
Fig. 38, 38a, 38b, 38c, 39, 59a, 39b, 39e, 39d, 
yolk cells; 500 diam. 
sculpta. 
Ozotheca odorata, laid and 
Fig. 40, 40a, 40b, 40c, 40d, 40e, 
40f, 402, 40h, 40i, 40j, 40k, 401, yolk cells of Chelydra 
serpentina, laid June 20, opened Aug. 20, 1856; 500 
opened Aug. 4, 1852. 
diam. In all the figures from 36 to 401, a is the ecto- 
blast, # the mesoblast, ¢ the entoblast. 
Fig. 41. Profile, and fig. 41a, view from above, nat. size of 
an ege of Ozotheca odorata. Laid and opened Aug. 4, 
1852. 
Fig. 42. 
the thickness of the egg-shell and its membrane ; a, a’, 
Surface of ege-shell, 40 diam.; fig. 43, section of 
