THE GENERAL SIGNIFICANCE OF AMPHIMIXIS 197 



simultaneous variations, and it is questionable whether they 

 will make the continued existence of the plant under the 

 new conditions possible or not. It might easily happen, for in- 

 stance, that the plant, though it became larger and bore more 

 abundant blossoms, would be sterile, and therefore unfitted for 

 continued existence in a natural state. Variations are not necessarily 

 adaptations; the latter can never come about solely through direct 

 influence upon the germ-plasm. What direct influence upon the 

 germ-plasm could, for instance, make the hind-legs of a mammal 

 long and strong and the fore-legs short and weak? Obviously 

 neither an increase nor decrease in the food-supply, nor a higher or 

 lower temperature — in short, no direct influence, because all these 

 afiect the germ-plasm as a whole, and therefore cannot possibly 

 influence two homologous groups of determinants in opposite 

 directions. 



This, it seems to me, is only possible when amphimixis brings 

 about in one individual a favourable coincidence of the chance 

 germinal variations of the determinants of the fore- and hind-limbs ; 

 and just as it is with the two variations in this simple hypothetical 

 case, so it will be in the actual processes of adaptation where there are 

 involved numerous — we know not how numerous — variations essential 

 to a ' harmonious adaptation.' 



It need not be objected that the verj^ number of variations 

 necessary to a ' harmonious adaptation ' makes its occurrence im- 

 practicable; for it is the complete harmony of the parts that makes 

 the adaptation, and without tlais the individual was only imperfectly 

 adapted, and therefore incapable of survival. It is certainly not 

 mathematically demonstrable that this is the case, but as the whole 

 process of transformation which makes an old adaptation into a new 

 one begins with minimal fluctuations of the determinants, which 

 must first be brought by germinal selection to the level of selection- 

 value, and must then be subject to personal selection, so the whole process 

 goes on so gradually and by such small steps that the harmony of the 

 parts is maintained by functional adaptation during the individual 

 life in a great number of individuals. But these are just the 

 individuals which surN^ive in the struggle for existence, and at the 

 same time possess at every stage of the process tlie best combina- 

 tion of favourably varying determinants. As these favourable 

 variations are, in consequence of germinal selection, not mere isolated 

 variations of fluctuating importance, but variations in a definite 

 direction, the whole process of variation must persist in every single 

 part in the direction imposed upon it by personal selection. But 



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