PLATE XIII 

 Two EARLY STAGES OF CLEAVAGE OF THE EGG OF THE SEA-URCHIN, x 1000 (Wilson) 



FIG. i. "The section passes horizontally through the egg at the moment of division. In 

 the centre lies the mid-body, darker and somewhat ill-defined. On either side of this is a group 

 of 2-3 nuclear vesicles formed by the fusion of the chromosomal vesicles of the preceding stage. 

 The remains of the centrosphere, scarcely defined, surround the nuclear vesicles." 



FIG. 2. " Two-cell stage preparing for the second cleavage. 



"A typical karyokinetic figure is forming in each cell at right angles to that of the first 

 cleavage." 



