Hyhridization of Echinoids. 25 



During division the yolk and oil droplets seem forcibly pushed out 

 of the region of the amphiaster, which lies in a region of clear cyto- 

 plasm. As the cell passes into the telophases of division the yolk 

 and oil droplets are carried inward and again lie distributed uniformly 

 through the cell. 



Fig. 8, a, b, and c. Three successive sections of a first-cleavage 

 amphiaster. One heterotypic chromosome, 32-32. 



I 



<^ b c 



FiG.9, c, 6, and c. Three successive sections of a first-cleavage 

 amphiaster. Two heterochromosomes. One chromosome 

 divided and lagging at the center. In the anaphase plates 

 32-32. 



The chromosomes divide and move apart with great regularity; 

 lagging chromosomes are seen only rarely (figs. 9a and 96). Figures 

 6, 7, and 9 are of anaphase plates showing two of the double-armed 

 rods in each plate of chromosomes; in figures 8 and 10 but one of these 

 chromosomes of double width could be found. In figure 11a only 

 one section of the spindle is shown; in this egg no chromosomes of 

 double width could be found; there is, instead, a chromosome of 



