CELL SIZE AND NUCLEAR SIZE 91 
Figs. 1-6 Successive stages in the development of the egg of C. plana, showing 
the maximum sizes of the nuclei of the macromeres. Fig. 1, 4-cell, just before 
third cleavage; fig. 2, 8-cell, just before fourth cleavage; fig. 3, 16-cell, just before 
fifth cleavage; fig. 4, 24-cell, just before sixth cleavage in macromere 3D; fig. 5, 
42-cell, just before sixth cleavage in macromeres 3A-3C; fig. 6, Gastrula, just 
before seventh cleavage of the macromeres. 
