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THE AMERICAN NATURALIST [Vol. XLIX 



Suppose now that at the point of space where we have pro- 

 jected the center of forces there lies some element of the embryo, 

 such as a cell. The scientific routine will call this element the 

 "bearer" of the forces in question. 



But it is also possible that no element and no matter is to be 

 found at this point. 



The first impulse will be to search for some other element of 

 the embryo, situated elsewhere, that can act as such a center, by 

 irradiating certain "lines of force," which influence in some 

 manner the movements of the first considered element. "We will, 

 however, assume a case where no such element acting at a dis- 

 tance can reasonably be supposed. What now ? 



If the fundamental assumption holds true, that the factors 

 determining the movements of the element lie outside of itself, 

 we find ourselves confronted by the following alternative: 



Either the presumed factors have a bearer that is not cogniz- 

 able, or they have no material bearer at all ! 



It is clear that if we deny the existence of bearers that are 

 evidently perceptible, we can also exclude the possibility that 

 such bearers exist, but are invisible owing to their minuteness; 

 for the presumed center of forces lies according to our assump- 

 tion outside the organism; or in a district of it where there is 

 no formed embryonic matter at all. 



Thus under the circumstances our two alternatives signify 

 the same thing, for to say that there is a bearer of factors 

 that is cognizable solely as the factors themselves involves 

 a tautology; an assumption of the sort so well character- 

 ized by the French as a "hypothese gratuite." "While any one 

 is free to make such an assumption, no scientific use can be made 

 of it. Methodologically it is perhaps comparable to Kant's 

 "Ding an sich," which likewise must remain without empirical 

 content. 



As a fundamental postulate of biological (and especially of 

 embri/oloi/ical) research, there can therefore arise the concep- 

 tion of factors which, although spatial and localized in space, 

 have no material hearers, and as such may be denominated im- 

 material. 



Is such an idea indeed nonsense; something that proves the 

 obscurantism of its promoter ? 



I am well aware that the "immaterial" factor here presented 

 is far from coinciding with Driesch's Entelechy or with any 



