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THE AMERICAN NATURALIST [Vol. LI 



to speak of the ''episode of Darwinism" and of Das 

 Sterhelager des Danvinismiis.^^ The enzj^ne theory of 

 vital determination brings new life to the doctrine of evo- 

 lution by accidental variation and natural selection, first, 

 by showing that all fundamental variations should be dis- 

 continuous, or heterogenetic, as demanded by the muta- 

 tion theory of De Vries, and second by revealing the exact 

 mechanism of the production of these variations. The 

 discontinuity follows from the existence of qualitative 

 gaps between all specific chemical substances, such as 

 those making up the system of genetic enzymes. The 

 mechanism of production of variations is simply that of 

 the initial production of any new chemical individual, i. e., 

 the fortuitous encounter of the appropriate molecules 

 with the right relative orientations and at the correct 

 speeds {vide supra). The "chance" nature of variation 

 thus is made to depend upon that "molecular chaos" 

 which is so very familiar to all physicists, but the impli- 

 cations of which for biology have thus far been largely 

 neglected. 



A moment's thought will show that, on the basis of the 

 enzyme theory, variation should be additive, since an 

 autocatalytic individual, once established, will tend auto- 

 matically to maintain itself. The complete elimination of 

 such individuals will occur only through the destruction 

 of the entire germinal mosaic of which they form a part, 

 an effect accomplished by natural selection unless the new- 

 enzyme is in harmony with functions which preserve the 

 organism. It is very important to bear in mind that the 

 catahi:ic complex which is supposed to underlie organic 

 development and regulation has been determined in its 

 nature by excessively exhaustive practical tests and, as a 

 complex, by nothing else. It is therefore not surprising 

 that the practical delicacy of the regulation which it actu- 

 ally subserves should be very great. 



In other papers, I have discussed somewhat in detail 

 the bearing of the enzyme theory upon the problem of the 

 origin of life. On the basis provided by this theory, the 



82 See Kellogg, V. L., "Darwinism To-day," 1907. 



