HEREDITY AND ENVIRONMENT 189 



cannot in the end show phenomena as the result of known 

 factors. Thus ultimate explanation is not explanation 

 at all. We cannot yet resolve final physical laws, and 

 therefore ultimate physics can only be called descriptive. 

 It is true the phenomena may in the end be ranged under 

 mathematical conceptions ; but mathematical reasoning is 

 not science in the strict sense. It is abstract illustration 

 of theoretic possibilities, and thus akin to pure logic. The 

 theory of Weismann, if it has any foundation, must be 

 capable of resolution, and may not be looked on as a quasi- 

 mathematical or purely verbal illustration of possible 

 mechanism. The effort of the neo-Darwinians to dispense 

 with his terminology is, indeed, not sound. What they 

 should have done, and what remains to be done, is to see 

 if his terms will bear translation into measurable factors. 

 This, I think, can be achieved but, if it can, the " nature " 

 of the germ-plasm will disappear and theoretic deter- 

 minants must disclose themselves as hormones, enzymes, 

 catalysts, and successively formed internal secretions, by 

 which each early cell-change or later embryonic or adult 

 development is actually determined. As held, the theory is 

 but a form of the " Absolute " conditioned purely by natural 

 selection. It may appeal to some philosophers, and to those 

 whose tendency is to short-circuit explanation by the hasty 

 use of final definitions ; but it might at least give pause to 

 its adherents to observe that anatomists, physiologists, 

 palaeontologists, and many others work habitually on the 

 theory that, whatever the mechanism, modifications can 

 be transmitted. It is true they may agree with the orthodox 

 biologist that in such cases the nuclear contents of the 

 reproductive cells are altered ; but they would certainly 

 add that such an alteration must be in the nature of an 

 addition, subtraction, or new combination of substances of 



