DEVELOPMENT BY NATURAL SELECTION. 105 



the inorganic world. Another view of the matter is, 

 however, equally possible ; and, to me at least, the 

 fact of evolution seems to lead, not towards reduction 

 of the organic to the level of the inorganic, but, on the 

 contrary, towards the raising of the inorganic to the 

 level of the organic. Let us, therefore, examine the 

 nature of Darwin's argument more closely, and in the 

 light of modern physiology. 



In the first place, the argument assumes the fact of 

 hereditary transmission, and that variations, in whatever 

 way they arise, are capable of being transmitted. A 

 variation not capable of being transmitted to offspring 

 would be of no account in Darwin's argument. The 

 true significance of the part played by hereditary trans- 

 mission in the Darwinian theory has, I think, hitherto 

 escaped due recognition. 



Let us picture to ourselves what a living adult 

 organism, or even a germ-cell, is on the mechanistic 

 theory. It is a structure, made up of molecules of 

 albumins and numerous other chemical substances, the 

 whole being so arranged that it reacts to the environ - 

 . ment in such a way that its characteristic life-history 

 tends to be fulfilled. It differs from simpler inorganic 

 structures in its greater complexity ; but if we knew 

 not only the nature and properties of the constituent 

 molecules and the action on them of the physical and 

 chemical environment, but the manner in which they 

 are arranged, we could predict the behaviour of the 

 organism. 



Now let us see what conception of hereditary trans- 

 mission is possible on such a theory. In the process 

 of reproduction an organism, whether it be an adult 



