CELL SIZE AND NUCLEAR SIZE 95 
Fig. 21 Centrifuged thirty minutes; fixed at once. Centrifuged during the 
second cleavage, which was thus made very unequal, two of the macromeres 
(A and D) containing all the yolk and the other two (B and C) being small and 
purely protoplasmic. 
Fig. 22 Centrifuged thirty minutes; fixed twenty-one hours later. The second 
cleavage was suppressed. Two spindles for the third cleavage are present in each 
cell, but the cell body shows no signs of division. 
Fig. 23 Centrifuged thirty minutes, during the second cleavage; fixed six hours 
later; two of the macromeres are small and protoplasmic; tetrasters are present in 
the other two. 
Fig. 24 Same slide as preceding. All of the macromeres have given rise to 
normal micromeres of similar size, although two of the macromeres are small and 
purely protoplasmic while the other two are large and contain much yolk and little 
cytoplasm. 
