2OO BARBARA HEFFXER. 



36, always counting the two arms of the Y-shaped chromosome 

 as one. 



Although I did not have very much material I was never- 

 theless able to trace the V-shaped chromosomes in the 2-, 4-, 

 8-, 12- and 16- to 32-cell stages. 



. . . ..;" 



O ~" O rt Q n O 



n * o o 



o O o o 



o o o a 



6a 6b 7 



FIG. 6. FIG. 7. 



Fig. 8, a and &, shows a metaphase from a 2-cell stage, with 

 the three V-shaped chromosomes distinguishable by their char- 

 acteristic splitting figures, which are fully explained below. 



Fig. 9, A and B, represents two adjoining cells of a 16- to 

 32-cell stage. In cell A, gb, we see three V-shaped chromosomes 



gfll 



8a 



. 



8b 



FIG. 8. 



and the two long ones. In B, gc, we see again two of the V-- 

 shaped chromosomes; and in gd the third one. The two long 

 ones are distributed between c and d. The chromosomes in 

 this stage are so small and crowded together that an accurate 

 count of their total number is impossible. 



The figures 10-15, enlarged 4 diameters and in publication 

 reduced one half, show splitting, or metakinesis, stages of the 



