.PLATE 1 



EXPLANATION OF FIGURES 



Chaetopterus. Susceptibility gradients in egg and larva 

 1 to 5 Susceptibility gradient in eggs thirty minutes after fertilization in 

 HgCla w?/500000. 



6 The beginning of swelling and cell separation in twenty-four hour stage. 



7 to 9 Later stages of cell separation in twenty-four hour stage. 



10, 11 Early and later stage of disintegration in fully ^developed larvae. 



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