EMBRYOLOGY OF THE TURTLE. Part III. 
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of the allantois, in the interior of the body, has swollen, and forms a broad, pear- 
shaped sac, (Pl. 25, fig. 1, n°, fig. la, n°) the urinary bladder. The tissue of the 
exterior portion of the allantois is composed of very large and thick-walled but trans- 
parent cells, (Pl. 9a, fig. 30, 50a; Pl. 18, fig. 5,) with multitudes of faint gran- 
ules for contents (Pl. 9a, fig. 50). The muscles in various parts of the body 
are in different degrees of development; those of the foreleg are highly, but not 
fully, developed, and show a very distinct fibrillous structure (Pl. 19, fig. 25, a, 6); 
those of the dorsal arch (PI. 19, fig. 25) are as yet composed of more or less 
elongated cells, (a, 6,) each of which contains a single large granulated mesoblast ; 
these cells resemble very much the cartilage cells (c) of the dorsal arch. The 
tendons in the legs have a marked fibrous structure (PI. 19, fig. 26, 26a). 
The cells of the terminal bone (Pl. 21, fig. 21) of the toes are quite large 
and sharply polygonal, and each contains a large mesoblast and several entoblasts 
(fig. 21a). The cells of the horny sheath (fig. 20, a) of the claw are very 
large, irregularly polygonal, and transparent, and contain a single small mesoblast 
(fig. 20a, 20b, 20c). The cells of the skin at the base of the claws, (fig. 20, 0’) 
and those (4) which continue under it, are quite large, polygonal, and each con- 
tains a single mesoblast and entoblast, besides a few scattered granules (fig. 20d). 
The next phase (Pl. 18, fig. 2, 4, 4a, 10, 10a, 10b, 10c, 10d, 10e, 10f; PI. 
20, fig..3, 8a, 7, 7a, 95 PL 19, fig: 27, 27a, 29, 29a, /30,..31, 33, 345 35)485a5 
Pl. 20, fig. 18; Pl. 22, fig. 5, 6, 6a, 6b) is the last before the embryo is hatched. 
A few external features, peculiar to certain families, and not noticed in the last 
phase, require now to be noticed; otherwise there is not any appreciable difference 
in the external appearance of the embryo. By this time the shield of many of 
the Emydoide is covered by a beautiful granular embossment (Pl. 18, fig. 10d, 10e, 
10f). The embryo, at the same time, is perfectly straight, in all oval eggs, (Pl. 18, 
fig. 10, 10a, 10b, 10c,) and not bent upon itself, as happens in round eggs (PI. 15, 
fig. 1, 2). In the latter case, at least among Chelydroidx, the embryo has not the 
power to retract its head or feet, except for a short distance; whereas in Emydoidee 
only two thirds of the head projects beyond the shield, and the feet are hidden 
under the latter, and the edge of the shield is very much bent downwards when 
the embryo is ready to hatch. The beak, (Pl. 25, fig. 9, 6/,) in all Turtles, is very 
prominent and sharp. The eyes may be closed as readily as in the adult. The 
cells of the epidermis (Pl. 20, fig. 18, right half) are large, sharply polygonal, 
and have thick walls. Underneath the epidermis is a layer of very large, thin 
walled, excessively hyaline, polygonal cells, each containing a large patch of pig- 
ment of a more or less deep black color (fig. 18, left half). The heart, (Pl. 25, 
fig. 3, h,) the liver, (fig. 3, 7, 7, fig. 3a, 7, 7,) the intestine, (fig. 3, n’, 3a, n’,) and 
the lungs, (fig. 5a, ¢,) are in nearly the same condition as in the last phase. 
