EXPLANATION OF PLATE. 



All figures were drawn with the aid of a camera lucida under a Zeiss Apoc. 2 

 mm., Oc. 4. 



1. An early stage in the formation of the first polar spindle before the chromatin 

 granules have fused into large masses. 



2. A stage about one-half hour later than Fig. I. The spindle has become barrel- 

 shaped and the chromatin granules are fusing into large masses to form the chro- 

 mosomes. 



3. Twelve irregularly shaped chromosomes have differentiated from the chromatin 

 masses and lie scattered along the spindle. 



4. Spindle parallel to the surface of the egg. The chromosomes have elongated 

 and many of them show a median knob. C.M., chromatin mass outside the spindle. 



5. About the same stage as Fig. 4. Chromosomes of very different sizes are found 

 on the spindle. 



6. Typical "oiselet" stage. 



7. Chromosomes in various stages of development on the same spindle. In some 

 of the chromosomes the splitting for the first maturation division can be seen while 

 the polar arms are still present. 



8. Section showing the growth of the lateral arms of the chromosomes at the 

 expense of the polar arms. 



9. The V-shaped chromosomes after the disappearance of the polar arms. 



10. An equatorial section of a spindle at the stage of Fig. 9. All twelve chro- 

 mosomes are present. 



11. Equatorial section. The notched ends of some of the chromosomes indicate 

 the direction of the first maturation division. 



12. Equatorial section. The first maturation division is completed and the second 

 maturation division is indicated in some cases. 



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