The Development of the AlHgator 22-^ 



which a Hberal grant of money to defray the ex- 

 penses of the expedition was received. 



The writer also desires to express his appreciation 

 of the numerous courtesies that he has received 

 from Dr. Samuel F. Clarke, especially for the loan 

 of several excellent series of sections, from which a 

 number of the earlier stages were drawn. 



In preparing the material several kinds of fix- 

 ation were employed, but the ordinary corrosive 

 sublimate-acetic mixture gave about the most 

 satisfactory results. Ten per cent, formalin, 

 Parker's mixture of formalin and alcohol, etc., 

 were also used. In all cases the embryos were 

 stained in toto with borax carmine, and in most 

 cases the sections were also stained on the slide with 

 Lyon's blue. This double stain gave excellent 

 results. Transverse, sagittal, and horizontal series 

 of sections were made, the youngest embryos being 

 cut into sections five microns thick, the older 

 stages ten microns or more in thickness. 



The Egg 



Figures i, \a (Plate VI.) 



The egg (Fig. i) is a perfect ellipse, the relative 

 lengths of whose axes vary considerably in the 

 eggs of different nests and slightly in the eggs of 

 the same nest. Of more than four hundred eggs 

 measured, the longest was 85 mm.; the shortest 

 65 mm. Of the same eggs, the greatest short 



