Figs. I-XV. Selected stages in the development of the egg. 

 In the text the stage represented by each of the figures is 

 designated by the Roman numeral of the corresponding figure. 

 The drawings are made from eggs which have been fixed, 

 stained, and mounted in balsam, and the eggs are therefore 

 treated as semitransparent objects. The stages during the form- 

 ation of the blastoderm are omitted, since nothing of importance 

 is visible on the exterior of the egg, x. 



