CONTENTS. 



Page 



I. Introduction i 



II. Literature 2 



III. Material and methods 6 



IV. Time relations of parturition, maturation, ovulation, insemination, and 



semination 15 



V. Ovulation 22 



VI. Size of egg 24 



VII. Observations on the maturation processes 25 



A. OScyte I 25 



1 . General description of stages 25 



Stage I. — Germinative vesicle 25 



Stage II. — Formation of first maturation spindle 26 



Stages III-V. — Development and division of first ma- 

 turation spindle 26 



Stage VI. — Telophase of first spindle, and the first polar 



cell 27 



2. Chromatin parts of first maturation spindle 27 



3. Achromatin parts of first maturation spindle 31 



4. Centrosomes, circumpolar bodies, and clear region 32 



5. Position and orientation of first maturation spindle 33 



6. Abstriction of first polar cell 34 



B. Oocyte II 35 



1 . General description of stages 35 



Stage VII. — Formation of second maturation spindle. . . 35 

 Stage VIII. — " Equatorial plate " of second maturation 



spindle 35 



Stage IX. — Division of second maturation spindle 36 



Stage X. — Telophase of second spindle and second polar 



cell 36 



2. Chromatin parts of second maturation spindle 36 



3. Achromatin parts of second maturation spindle 38 



4. Centrosomes, circumpolar bodies, and clear region 39 



5. Position and orientation of second maturation spindle. ... 40 



6. Abstriction of second polar cell 40 



C Ripe egg 41 



Stage XI. — The pronuclei 41 



D. Polar cells 41 



First polar cell 41 



Second polar cell 44 



VIII. Criticisms and conclusions 45 



.4. Material 45 



B. Methods 45 



C. Time relations 46 



D. Ovulation 49 



E. Size of egg 50 



iii 



