538 EMBRYOLOGY OF THE TURTLE. Part III. 
In consequence of these folds, and owing also to the growing transparency of the 
annular depression which forms the area pellucida, (Pl. 11, fig. 2, ¢) the embryo 
has a very prominent aspect, underlaid as it is by a dark background. 
In an immediately succeeding phase, (PI. 11, fig. 8,) the horns above men- 
tioned are overlapped by the more prominent central cone, (Pl. 11, fig. 3, a’,) 
and the depression at the caudal end is quite deep (Pl. 9e, fig. 38, a; Pl. 11, 
fi 
more depressed (Pl. 9e, fig. 3a, v) than before, and the whole embryo is strongly 
9 
g. 3, a) and broad, fully as much so as the cephalic one; the sides also are 
arched, and tapers towards the end where the three conical eminences crowd together 
(Pl. 11, fig. 3, a’). Here the lunate depressions (Pl. 11, fig. 3, ¢, ¢) are no longer 
confined to the width of the original embryonic disc, but extend even to the edge 
of the area pellucida, so that the latter is divided into four nearly equal por- 
tions or fields, namely, two lateral areas, (PI. 11, fig. 3, a*-a‘,) slightly sunk, and 
two deeply depressed ones, (c, ¢,) and terminates by a sudden bend (Pl. Ye, fig. 
3, d, d, 3a, d, d) at the outer edge, where it joins the more peripheric part of the 
germinal layer (PI. I1, fig. 3, d)." The distinctness of these four regions depends 
upon the greater or less degree of foldmg of the edge of the embryonic disc, 
the base of attachment of the amnios. In these last two phases the subsid- 
iary layer (Pl. 9e, fig. 5, d, d, 3a, d, d) is not so thick as before, and does not 
follow so closely the upward curvature (Pl. 9e, fig. 3, ¢, ¢, 3a, ¢, ¢) of the ger- 
minal layer, where it extends over the area pellucida; but, stretching outwardly 
with a long bend, (fig. 5, ¢, 3a, d,) leaves a considerable space (c’, c'!) between itself 
and the sudden fold of the layer above. This structure, with the thinning of the 
subsidiary layer and the presence of the infiltrated albumen, accounts for the dark 
but transparent appearance at this region. 
Next, we see the sides of the embryo so folded in (PI. 11, fig. 4) that the 
neighboring areas are brought down to a level with those at each end, so that 
the embryo rests like a dome on a short, broad pedestal in a circular valley. We 
(Pl. 11, fig. 10). Like the cephalic hood, the caudal fig. 9b,) and that its upper side, nearly touching the 
hood is well marked by the sudden bending down- highly arched back, follows its curve along the whole 
wards of the posterior end of the embryo, and the length. A view in front (PI. fig. 10c) shows that the 
sides of the body also are curved down. However, middle of the back is sunk, probably indicating either 
upon close scrutiny, we find that the cephalic hood a fold, or a tendency to form a regular primitive fur- 
has developed just as in the monstrosity of Ozotheca row. In all these examples of monstrosity, the clear 
odorata. Here the blind sae is nearly cylindrical (PI. dark space, the area pellucida, is as normally devel- 
11, fig. 10a) and much narrower than that of Ozo- oped, and appears to be as natural, as in the healthiest 
theca, but, like the latter, reaches to the caudal end of embryos at this age. (Compare Pl. 11, fig. 9, and 10, 
the embryo, and expands at the mouth like a trumpet. with fig. 2, 3, 4). 
In a longitudinal section (fig. 10b) we see that the 1 Tn Pl. 11, fig. 3, the letter a should be d, as in 
blind sae is not so flattened as in Ozotheca, (PI. 11, fig. 2. 

