PHYSIOLOGICAL CHARACTERISTICS OF AXIATE PATTERNS 133 



CLEAVAGE STAGES AND EARLY BLASTULA 



In early cleavage stages of Strongylocentrotus purpuratus and S.francis- 

 canns rate of reduction decreases basipetally, but the differential is slight; 



A 



B 



C D 



Fig. 44, A-D. — Dye-reduction gradient in early cleavage stages of Strongylocentrotus 

 franciscanus; arrows indicate direction of progress of reduction (from Child, 1936(7). 



A B 



Fig. 45, A, B. — Dye-reduction gradient in early echinoid blastulae; optical sections, A, 

 Strongylocentrotus purpitratiis; B, Dendraster excentriciis (from Child, 1936a). 



no evidence of more rapid reduction in the micromeres at the basal pole,- 

 either during their formation or in following cleavage stages, has been ob- 

 tained (Fig. 44). Results of a few observations on susceptibility of these 



