The Development of the Alligator 229 
In most—probably all normal—eggs a white 
band appears around the lesser circumference a 
short time after being laid. This chalky band, 
which is shown at about its maximum development 
in Fig. 1a, is found, on removal of the shell, to be 
caused, not by a change in the shell, but by the 
appearance of an area of chalky substance in the 
shell membranes. Clarke thinks this change in 
the membrane is to aid in the passage of gases to 
and from the developing embryo. Generally this 
chalky area forms a distinct band entirely around 
the shorter circumference of the egg, but sometimes 
extends only partly around it. It varies in width 
from about 15 mm. to 35 mm., being narrowest at 
its first appearance. Sometimes its borders are 
quite sharp and even (Fig. Ia); in other cases they 
are very irregular. If the embryo dies the chalky 
band is likely to become spotted with dark areas. 
The shell and shell membrane of the egg of the 
Madagascar crocodile are essentially the same as 
those just described, except that the shell is some- 
times pierced by small pores that pass entirely 
through it. The same chalky band surrounds the 
median zone of the egg (78). 
The white of the egg is chiefly remarkable for its 
unusual density, being so stiff that the entire egg 
may be emptied from the shell into the hand and 
passed from one hand to the other without danger 
of rupturing either the mass of albumen or the 
enclosed yolk. The albumen, especially in the 
