192 



DEVELOPMENT OF THE FROG'S EGG 



Wrinkles of egg, 33. 



Weismann, theory of heredity, 14. 



qualitative nuclear division, 129. 



qualitative division of nucleus, 



134. 



Wetzel, double embryos, 118, 119. 

 Whitman, theory of embryo, 136. 

 Wichmann, pronephros, 158. 

 Wilson, E. B., amphioxus, 127. 



Yolk-granules, absorption of, 141. 

 Yolk-plug, withdrawal of, 140. 

 Yung, effect of light, 169, 170. 



Ziegler, embryos, 61. 



Zoja, isolation of blastomeres by, 132. 



