NATURAL SELECTION 129 



VIII 



VARIATIONS AND ADAPTATIONS : LIMITATION OF THE RANGE 

 WITHIN WHICH CHANCE HAS FREE PLAY 



I have now shown that it is not mere matter of chance into 

 what environment the young progeny are pitched. Low down in 

 the animal world their surroundings are decided by undeviating 

 instinct. By instinct the moth lays its eggs on the right plant, 

 with the result that her caterpillars find themselves in the best 

 environment. At a higher level animals have gained plasticity 

 and power of accommodation without sacrificing the advantages of 

 rigidity. Parental leading, or the example of his fellows of the 

 same flock, ensures that the young thing finds himself in as good 

 an environment as is obtainable. As the generations pass, the 

 environment, thus chosen, changes so gradually that by the help 

 of favourable variations the best representatives of each generation 

 are able to cope with it. Chance is to some extent driven out 

 of the field : the animal, be he high or low in the scale, seeks the 

 environment that suits him. 



But there are the variations to be considered. Are they Adapta- 

 matter of chance ? The Lamarckian says they are due to tlons due 



J to mere 



external influences. But he cannot help us, since we have coincid- 

 found that such influences have nothing to do with the matter ; er 

 the environment cannot bring pressure to bear upon living 

 organisms to make them vary into all their adaptive forms. 

 But does the organism, owing to its own essential nature, aim, 

 so to speak, at some peculiarity in its surroundings and so pro- 

 duce an adaptive variation ? The evidence goes to show that 

 adaptations are mere coincidences, mere chance hits. This 

 evidence, since very conflicting interpretations are based upon 

 it, I must give, however briefly. 



Change in external conditions conduces to variations both The en _ 

 in animals and plants, but the variations are not necessarily vironment 

 adaptations. In plants, removal to a rich soil, with ample Sate"*" 

 room to grow, often results in surprising deviations from the variability 

 form of the original stock. The conditions, almost beyond a 



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