BODY SIZE AND CELL SIZE 



175 



Figs. 8 to 10 Corresponding stages in the eggs of C. f ornicata, C. convexa, and C. 

 adunca, drawn to the same scale. The blastomeres correspond cell for cell except 

 that one additional ectoderm cell (the basal cell in the posterior arm of the cross, 

 shaded by transverse lines) is present in C. adunca (fig. 10) which is not present 

 in the other species. There are present: 39 ectoderm cells (40 in C. adunca), 

 6 mesoderm cells, 7 endoderm cells. 



