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Cuap. II. FOLDINGS OF THE EMBRYONIC DISC. 
(Pll, wigs deaRindoedig., 1452355 6501 6agcl7, Vay ivb5, Pk 20;-fig. 3, 13,, 13a, 
14 ilday Voli ieee ye 10,011.12, 138, 13a, $17, 18;. 18a, 18b,18¢; 19, 
Boy) Spal eebL eho welas Ib, 2,3, 3a, 4, 4a, 8 8a; PL 23, fig 4, 4a, 5, 6, 
7, 8, 9, 10, 11) represent the condition of the young Turtles during a period 
extending over nearly three months and a half after they were hatched. The 
organs of but one species (Chelydra serpentina) are represented here. 
The cavity of the intestine (PI. 17, fig. 1) is totally shut off from the yolk 
sac, but the wall of the former is not detached from it. There are two dis- 
tinct muscular coats (Pl. 21, fig. 11, d, 18, ¢, d, 19, ¢ d) in the intestine, the 
fibres of which run transverse to each other. The cells of the muscular layer 
(Pl. 21, fig 11, d) of the cesophagus are excessively long, and tapering at each 
end (fig. 13, 15a). The epithelial layer of this part of the intestine is more 
compact (PI. 21, fig. 11, a, 4). At the base of the tongue there are no vibra- 
tile cilia, (Pl. 21, fig. 10,) but the cells resemble those at the posterior end of 
the intestine (Pl. 21, fig. 18, 18a, 18b, 19). The glands of the stomach are con- 
siderably elongated and convoluted, (Pl. 21, fig. 17,) and the wall (c, d) of each 
is very thick, beimg composed of three or four layers of cells, continuous with 
the epithelial layer (a) of the surface of the stomach. The epithelial layer of 
the long intestine (Pl. 21, fig. 18, 18a, 18b, 18c) and of the rectum (PI. 21, 
fig. 19) is now composed of five or six layers of superposed cells. The carti- 
laginous rings (Pl. 20, fig. 5, 2) of the windpipe are much broader than the inter- 
vening fibrous tissue (a). The cartilage cells (Pl. 20, fig. 3, 4) are widely sep- 
arated from each other, just as in all permanently cartilaginous bodies. The 
epithelial cells (Pl. 20, fig. 15, 15a, 15) of the urmary bladder can hardly be 
distinguished from those of the long intestine and of the rectum. The muscular 
walls (Pl. 20, fig. 16) of the bladder are highly developed; the fibres are very 
distinct, and run in every possible direction. The cells of the smooth muscles of 
this organ vary in their proportions at different depths (fig. 14, 14a); those 
more interior being the longer ones. The contents of the bladder, seen by 
incident light, have a dead white color, by transmitted light a fuscous color; and 
consist principally of large, dead white flakes, (fig. 17,) composed of very minute 
granules, and a few bodies which appear to be epithelial cells, in various stages 
of decomposition. 
The brain (Pl. 23, fig. 4, 4a, 5, 6, 7, 8, 9, 10) fills the cranial cavity as 
completely as in the adult. It is more elongated, and not so deep, as in the 
last stage (Pl. 25, fig. 3). The Schneiderian membrane (fig. 4, 11, and wood- 
eut 3, b, w-e.' 11, a) is more expanded vertically, and the olfactory nerve (fig. 4, 
1 Tn these references, “ w-c.” is the abbreviation for wood-cut. 
