No. 2.] EMBRYOLOGY OF THE AMERICAN ALLIGATOR. 191 



the shell is partly chipped off, showing the inside chalk-white 

 zone. 



The white of the egg has the consistency of a very thick 

 jelly, is very clear and transparent, and is so firm that the whole 

 egg, when perfectly fresh, may be turned out of the shell and 

 shell membrane, and transferred from one hand to the other 

 without breaking, and with but slight change of form. The 

 chalazae, as in the eggs of the other reptilia, are absent. There 

 is, of course, no need of them in eggs which are not moved or 

 turned, in which the yolk is surrounded by such a firm mass of 

 white, and which are carefully buried. The white lies mostly 

 at either end of the shell, but extends also in a thin layer 

 between the yolk and the sides of the shell ; and in this median 

 area the white is more closely attached to the shell membrane, 

 being after the first few days very firmly united to it at the 

 edges of the chalk-white zone. Fig. 6, PI. IX, represents an 

 egg from which the yolk has been removed : the consistency of 

 the white is shown by its hanging in heavy folds on either 

 side. This shows the middle chalk-white zone on the upper 

 side of the shell, and also that the white is attached to the shell 

 membrane at the outer edges of this zone. 



Fig. 48, PL XIII, shows the position and place of attachment 

 of the white. The white has here been removed from one end ; 

 the stronger transverse lines in white are the lines of union with 

 the shell membrane : a thin pellicle of white stretches across 

 the median area. 



The yolk holds a median position in the egg, is spherical, a 

 very light pale yellow, and so large that it almost touches the 

 shell membrane about the mid-line (see PI. IX, Figs. 7, 8). 



The germ in most of the eggs opened during the first few 

 days of incubation was at one pole, as shown in Fig. 8, PI. IX. 

 About the germ is a considerable area having a more or less 

 mottled appearance, and bounded by a sinuous white line. In 

 some instances the germ was found upon the side of the egg, as 

 shown in Fig. 7, PI. IX. Somewhat later, toward the end of 

 the first week of incubation, the germinal area is found moving 

 from the polar region to the side, as shown in Fig. 9. Finally 

 it comes quite to the side, as shown in Figs. 10 and 1 1. 



The polar position at first is an advantageous one, on account 

 of the greater protection afforded by the large mass of gelati- 



