CONTENTS 



Some Studies on Differentiation and Development of tlie 

 Oocyte 

 W. S. Vincent 1 



Specific Egg and Sperm Substances and Activation of the 



Egg 

 Charles B. Metz 23 



Preliminaries to Fertilization in Mammals 



C. R. Austin and M. W. H. Bishop 71 



Some Aspects of Mammalian Fertilization 



M. C. Chang 109 



Morphology of Fertilization: Acrosome Filament Forma- 

 tion and Sperm Entry 

 Arthur L. Col win and Laura Hunter Colwin 135 



Studies of Proteins of Sea Urchin Egg and of Their Changes 

 Following Fertilization 

 Alberto Monroy 169 



Nucleocytoplasmic Relations in Early Insect Development 



R. C. von Borstel 175 



Nuclear Transplantation, a Tool for the Study of Nuclear 

 Differentiation 

 H. E. Lehman 201 



Morphogenesis and Metabolism of Gastrula-Arrested Em- 

 bryos in the Hybrid Rana pipiens $ x Rana sylva- 

 tica $ 

 John R. Gregg 231 



Some Observations on Cytoplasmic Particles in Early 

 Echinoderm Development 

 John R. Shaver 263 



Early Determination in Development under Normal and 

 Experimental Conditions 

 Silvio Ranzi 291 



vii 



