The Early Development of the Pigeon's Egg. 



61 



Fig. 51. — Photograpli of a pigeon egg at 11.00 a. m., fifteen hours after 

 fertilization. An earlier stage of the same egg is shown in Fig. 50. This 

 photograph is taken from a whole mount, with reflected light. The light areas 

 at the anterior and right side are due to breaks in the yolk. The light irregu- 

 lar circle is caused by a crack in the material. 



