iv CONTENTS. 



VIII. Criticisms and conclusions Continued. Page 



F. Maturation processes 51 



1 . Germinative vesicle 51 



2 . First spindle 51 



Chromatin 51 



Achromatin 55 



Centrosomes, circumpolar bodies, and clear region 56 



Position and orientation 57 



Division of first spindle and abstriction of first polar cell 59 



3 . Second spindle 60 



Chromatin 60 



Achromatin 62 



Centrosomes, circumpolar bodies, and clear region 63 



Position and orientation 63 



Division of second spindle and abstriction of second 



polar cell 64 



4. Polar cells 64 



5. Reduction 66 



IX. Summary of the principal results in the study of the egg of the mouse. ... 67 



Bibliography 69 



Explanation of plates 71 



