PLATE 6 



EXPLANATION OF FIOURES 



Differential acclimation and differential recovery 



40 to 48 Cases of apical acclimation after the more extreme degrees of dif- 

 ferential inhibition, in which the antero-posterior axis and bilateral symmetry 

 have been more or less completely obliterated. 



49 to 53 Cases illustrating the lower limits of differential acclimation after 

 extreme differential inhibition which has obliterated all axes except the apico- 

 basal. 



54 to 56 Differential recovery in early and late grastrulae and early pluteus. 



57 to 62 Cases of differential recovery after a considerable degree of dif- 

 ferential inhibition, showing rudimentary oral lobe as an apical outgrowth, and 

 a basal portion of ciliated band; antero-posterior axis and bilaterality more or 

 less completely obliterated: figure 62 from an exogastrula. 



63, 64 Cases of differential recovery with rudimentary oral lobe, but with- 

 out basal portion of ciliated band. 



65 to 67 Cases of differential recovery in which oral lobe does not develop, 

 mouth is apical and basal portion of ciliated band is present; in figure 67 the en- 

 teron has separated from the blastopore region and a lateral anus has formed. 



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