140 THE EVOLUTION THEORY 



If we look into the matter more carefully, we see that it is not 

 strictly true to say that germinal selection alone brings about the 

 extinction of a species by cumulative augmentation of structures which 

 are already excessive; it is the incapacity of j)6Tsonal selection to Iceep 

 pace with the vnore rapid changes in the conditions of life and to 

 reduce excessive developynents to any considerable extent in a short 

 time. This would always be possible in a long time, for the deter- 

 minants of the excessive organ E can never be equally strong in all 

 the ids; they always fluctuate about a mean, however high this 

 mean may be. Here again it must still be possible that reducing- 

 divisions and amphimixis may lead to the formation of majorities 

 of ids with weaker ^'-determinants, and if sufficient time be allowed, 

 artificial selection could, by consistently selecting the individuals 

 with, let us say, weaker antlers, give rise to a descending variation- 

 movement. There are no variation-movements which cannot be 

 checked ; every direction can be reversed, but time and something 

 to take hold of must be granted. That was wanting in the case 

 of the giant stag, for it would not have been saved even if its antlers 

 had at once become a couple of feet shorter, and germinal selection 

 can hardly make so much difference as that. 



Analogous to hereditary deformities, and of special interest in 

 connexion with the processes within the germ-plasm, are ' sports' 

 variations of considerable magnitude which suddenly appear without 

 our being able to see any definite external reason for them. I have 

 already discussed these in detail in my Germ-plasm, and have shown 

 how simply these apparently capricious phenomena of heredity can 

 be understood in principle from the standpoint of the germ-plasm 

 theory. 



The chances of the transmission of the saltatory variation will 

 be greater or less according to whether the variation of the relevant 

 determinants involves a bare majority of ids or a large majority, for 

 the more ids that have varied, the greater is the probability that the 

 majority will be maintained throughout the course of ensuing reducing 

 divisions and amphimixis, that is, that the seeds of the plant will 

 reproduce the variation, and will not revert to the ancestral form. 

 Although one of the most satisfactory results of the id-theory lies 

 precisely in the interpretation of these conditions, I do not wish 

 to enter into the matter here, but will refer to the details in my 

 Germ-plasm, published in 1894, which I consider valid still. At 

 that time I had not formulated the idea of germinal selection, but 

 the explanation of the occurrence of such sport-variations which 

 I gave was based upon the assumption of nutritive fluctuations in the 



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