500 EMBRYOLOGY OF THE TURTLE. Part III. 
Now, unless one spends day after day and week after week in the fields in 
the neighborhood of the breedmg grounds and catches each day a great number 
of Turtles of different species, in order to ascertain the presence of eggs in the 
oviducts, (as may very readily and confidently be done by inserting the finger 
between the shield and the plastron, just in front of the hind legs,) and then 
having marked them lets them go again to remain free and in a natural and 
untrammelled state until they can be taken up again perhaps within the next 
few hours or the next day, it is utterly impossible to determine when the eggs 
enter the oviduct, and how long they remain in this organ. Although we have 
seen many Turtles laying their eggs in confinement in a large yard where they 
were kept well fed and furnished with plenty of water, which is very essential to 
some species, and although these eggs developed their embryos, still they were 
always retarded, both as to the time of their being laid, and to the advancement 
of the young itself By reference to the tables,' it will be seen that in two 
instances the eggs of Nanemys guttata and of Chelydra serpentina were retained 
in the oviduct nearly a whole month beyond the usual time of laying, in con- 
sequence of the confinement of these animals. The former having dug, as usually, 
a hole with its hind legs, at last dropped its progeny into the excavation, and 
covered the same so as to leave no trace of its operations; but the latter was 
opened, and found still retainmg its brood. 
As to the time of the day at which Turtles lay, there have been not more than 
three different species of so many distinct genera observed throughout the laying 
season; but, as a great many were seen always laying im the same part of the 
day, there can be no doubt that different species lay regularly at different times. 
Chrysemys picta and Nanemys guttata deposit their eges in the evening, from six 
to halfpast eight o'clock, and Chelydra serpentina in the morning, from four to 
twelve midday. Ozotheca odorata was seen laying but once, namely, at halfpast 
eight in the evening. 
In this connection it will be most proper to give some account of the kind 
of nests which these animals make, and of their manner of proceeding in the for- 
mation of the same. We have already alluded briefly to the laying of one spe- 
cies, (Nanemys guttata,) in confinement; but would say in addition, that this spe- 
cies, as well as Chrysemys picta, digs a perpendicular hole, whereas Chelydra_ser- 
pentina excavates at first directly downwards and then laterally, so that the widest 
part of the hole, in which the eggs are deposited, is on one side of the exter- 
nal opening of the nest. Hence a stick thrust straight into the mouth of the 
nest would not touch the eggs, which are laid in the lateral dilatation of the 
1 See p. 498 and 499. 
