PLATE 4 



EXPLANATION OF FIGURES 



35 First maturation spindle rotated so that its long axis comes to lie per- 

 pendicular to a tangent to the surface of the egg at its point of contact. In this 

 case the male centrosome is undivided. (X 1700) 



36 Polar view of metaphase plate of first maturation spindle, showing eigh- 

 teen chromosomes. (X 4050) 



37 Lateral view of spindle of the same age, showing di-tetrad nature of the 

 chromosomes. Sjjindle fibers no longer in bundles. (X 4050) 



38 Lateral view of very late metaphase plate showing longitudinal division 

 of the chromosomes. (X 4050) 



39 Primary oocyte, showing the spindle in the anaphase condition and the 

 sperm accompanied by the male centrosome in process of division. (X 1700) 



40 Lateral view of anaphase spindle of first division, showing tetrad nature 

 of the daughter chromosomes. (X 4050) 



41 Polar view of anaphase group of the first maturation division. (X 4050) 



42 Late anaphase of the first maturation division. (X 1700) 



43 Cutting off of the first polar cell. (X 1700) 



44 First polar cell completed. Reorganizing of inner half of spindle figure. 

 (X 1700) 



45 'Interkinetic period. ' Formation of a transient nuclear membrane and the 

 division of the still persistent female centrosome. (X 1700) 



592 



