No. 559] DOCTIUXES HELD AS VITALISM 



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varied ways; it still moves toward the earth. We may 

 change the material, substituting lead, brass, stone, wood; 

 it still moves toward the earth. We may change both 

 form and material in most radical ways; it still moves 

 toward the earth. In a clock that keeps time we may sub- 

 stitute iron wheels for brass ones; we may remove a 

 number of the wheels, and substitute others in different 

 number and form and made of different material, and 

 still have the clock keep time. A stream that flows to the 

 sea will still flow to the sea though its bed be altered in 

 many ways; if obstacles are interposed, it will dig be- 

 neath, or overflow, or go around, or carry the obstacle 

 away, and finally reach the sea. A microscope bringing 

 light to a focus may be made of lenses of different ma- 

 terials, in different forms, in different arrangements. A 

 diffraction grating may be substituted for a prism, in 

 order to separate the rays of light of different velocities. 



23. In all these cases it is evident: (1) that the partic- 

 ular changes made are such as do not affect radically the 

 particular action in question; (2) we could make changes 

 that would alter this action; (3) furthermore, in most 

 cases at least, the process gone through does differ in 

 certain respects after the change is made, although the 

 general result remains the same. Now, precisely these 

 same three statements can be made for the phenomena 

 in organisms. When we remove a part of the egg of the 

 sea urchin, or otherwise alter it, and it continues to de- 

 velop, it is evident (1) that the change made is one that 

 does not radically affect the development ; this is a mere 

 statement of the observed facts. But (2) we can readily 

 make an alteration that will prevent the characteristic 

 action, just as we can in the clock. No one, of course, de- 

 nies this : all that is necessary is to remove the nucleus, 

 or destroy its characteristic structure ; and other changes 

 will accomplish the same result. Again, (3) the proc- 

 esses after the egg has been altered are somewhat dif- 

 ferent from what they were before (as no one denies), 

 though the development takes in its main features the 



