Fig. 49, A-E. — Differential dye reduction in echinoderm gastrulae. Arrows show direction 

 of progress of reduction, their relative lengths, relative rates of progress; numerals i-j, adjoin- 

 ing certain regions, indicate the general time-order of reduction, with / as most rapid; two 

 numerals (/, 2; j, 4) adjoining the same region indicate individual variations in order. A, B, 

 Strongylocentrolus pjtrpuralus {S. franciscanus and Dendraster excentriciis similar); C-E, 

 Paliria {A, C-E, from Child, 1936a). 



