104 



DEVELOPMENT OF THE FROG'S EGG 



[Cn. X 



the apices of the spindle, must also be considered. The centro- 

 somes determine the position of the poles of the nuclear spindle. 

 Moreover, the position of apposition of the two pronuclei of the 

 egg may be a further factor in the first cleavage. 



THE DISTRIBUTION OF THE NUCLEI IN THE COMPRESSED 



EGG 



In the experiments recorded above, where the frog's egg is 

 compressed during the cleavage-period, the distribution of nuclei 

 in the protoplasm is different from that in the normal egg. 

 This is illustrated in the accompanying diagrams (Fig. 33). 

 Let us call the segmentation-nucleus A, and its first products 



