Embryonic Development of the Crocodile. 67 
have not yet succeeded in securing a specimen of this second 
species ; my remarks therefore refer exclusively to Cr. nilo- 
ticus, Laur. (madagascariensis, Grandid.). 
This animal is met with in all sizes, especially numerous 
on the sandbanks of the Betsiboka River, where, in the space 
of an hour, in rowing down the river, a hundred and more 
may be readily observed. The largest which I have yet 
measured was 13 feet in length, though individuals of consi- 
derably larger size occur. 
Oviposition commences in the latter days of August, and 
continues until towards the end of September *, after which I 
found that the eggs all contained embryos. Altogether rather 
more than one thousand eggs were submitted to examination, 
.derived from about thirty-five batches. In a few cases the 
number of eggs in the batch could not be exactly determined. 
The number of eggs in a batch varies between twenty and 
thirty. 
The nest consists of a pit excavated in the earth to the 
depth of about a foot and a half to two feet, with partially 
steep walls. At the bottom of the pit the walls are under- 
mined, and here the eggs are placed. ‘The floor of the pit is 
raised slightly in the middle, so that the eggs, as they are 
laid by the female, roll by themselves into the hollowed-out 
places. Very rarely one or two eggs are found lying in the 
middle of the pit, which may well be taken as proving that 
the mother does not herself push the eggs into the hollows 
with her feet, for in that case no eggs would ever be found in 
the centre of the pit. After the eggs are laid the pit is filled 
in, and no sign of it can be detected from above. ‘The old 
crocodile sleeps upon the nest, and this enables the natives to 
find the eggs, since they follow the tracks of the animal from 
the water. 
The shape of the eggs is extremely variable, and not even 
those of the same batch resemble each other completely ; 
many are elliptical, others cylindrical with rounded ends; 
two eggs were pointed at one end. In size they vary from 
54 to 9 centim. in length and from 4 to 5 centim. in breadth. 
The shell is white, thick, and hard, sometimes coarsely 
granular, sometimes smooth. 
Almost all the nests were dug in the dry white sand, a few 
in ground rich in humus, but in such a way that they could 
not be reached by damp. I must lay especial emphasis 
on the latter point, since freshly-laid eggs are peculiarly 
sensitive to wet. More than half the eggs which were 
* Oviposition does not appear to take place at the same time in all 
localities, since Keller mentions the month of January for Nossi-Bé, 
* 
