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THE AMERICAN NATURALIST [Vol. XLVII 



tution signifies the following experimental situation. If 

 an experimenter could have the egg of a starfish and 

 another of a sea urchin presented to him, knowing noth- 

 ing of their origin, could examine each so thoroughly as 

 to perceive all the perceptual characters, all the physical 

 diversities well known to exist between the two, and 

 could observe that one develops into a starfish, the other 

 into a sea urchin — he could not predict, when a similar 

 pair are again presorted, which would produce a starfish, 

 which a sea urchin (although it is admitted that he could 

 if he knew the origin of the two). Is there any plausible 

 ground for such a proposition? 



(b) As between these eggs from different organisms, 

 the assertion is that the diversities in what occurs are 

 not due to the present and observable differences in 

 physical constitution, these differences being supposedly 

 "not among the essentials." 



Now, this abandons experimental evidence and all 

 possibility of such, for it is well known that the eggs of 

 different organisms do show differences in constitution, 

 and that these differences are followed regularly by dif- 

 ferences in what happens, which is all that experimental 

 science can discover. 



55. The result of these two admissions is then to leave 

 without any possible empirical basis the idea that two 

 perceptually identical systems can give diverse results, 

 save only if there are ever cases with eggs of the same 

 organism where the "very great probability" spoken of 

 is not realized. All admit that the eggs of diverse or- 

 ganisms are perceptually diverse; Driesch admits that 

 the eggs of the same organism always do the same thing 

 under the same conditions "with very great probabil- 

 ity." Nothing then is left, so far as development is con- 

 cerned, but the substitution of this "very great probabil- 

 ity" for "certainty," as a basis for the idea that an ex- 

 perimental, perceptual, cause is ever lacking for any di- 

 versities in result; and so for that kind of vitalism which 

 requires and depends upon experimental indeterminism. 



