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SCIENCE 



[N. S. Vol. XXXI. No. 789 



uralists and philosophers together— for 

 better, for worse. 



Many other illustrations will occur to 

 every naturalist: for instance, the instinct 

 of the caterpillar to spin a coccoon that 

 serves as a protection not so much for itself 

 as for the future pupa, the instinct of the 

 spider to make a web to catch a prospec- 

 tive fly, or of a bird to build its nest for 

 eggs not yet in sight; the occurrence of 

 offensive odors or poisons, or of organs 

 that act as a passive defense for the ani- 

 mal as the spines of the hedgehog or of 

 the sea-urchin, or the colors of animals 

 that may at times serve to protect them. 

 Zoologists have, I think, often let their 

 imagination run riot concerning some of 

 these adaptations, but there remains 

 enough that is probable to satisfy the most 

 sceptical. 



I have said that we can not afford to 

 underestimate the directly adaptive re- 

 sponses shown by the body, and I have 

 intimated that these are only elaborations 

 of already existing functions. Let me add 

 that the naturalist has equally felt that 

 he can not aiford to neglect the lock and 

 key adaptations. The alliance between 

 philosophy and biology is due to the fact 

 that these contrivances are not the result 

 of primary, or directly causal relations, 

 but are secondary relations, which appear 

 to be removed from the province of phys- 

 ical problems in the sense that they are 

 supposed not to be the result of causal 

 interaction. It is in this aspect of the sub- 

 ject that chance and purpose bloom forth 

 in all of their significance and danger. It 

 is here, therefore, that it is our duty as 

 scientists to make careful inquiry into 

 what causes the lock to vary and what 

 the key and to discover, if possible, 

 whether there exists any mechanism to in- 

 sure that they shall continue to vary along 

 the same lines. 



Perhaps the following somewhat shop- 

 worn case may further illustrate my mean- 

 ing. 



The long coiled proboscis of sphinx 

 moths permits them to reach the juices at 

 the bottom of flowers with a tubular 

 corolla. The proboscis is fully formed 

 when the moth emerges from the pupa and 

 its use has no influence in increasing its 

 length. The proboscis is to the corolla 

 what the key is to the lock and yet the 

 lock can have no causal, i. e., direct influ- 

 ence in shaping the key. 



If we exclude the Lamarckian explana- 

 tion, we find many relations of this sort. 

 The speed of the hare bears no causal rela- 

 tion to that of the fox. We can not think 

 of the fox in the sense of a physical en- 

 vironment acting on the germ cells of 

 hares; yet without the fox the hare would, 

 we feel confident, never have developed 

 the long hind legs. In brief, the zoologist 

 has come to look upon contrivances of this 

 kind as the very essence of adaptation. 

 He finds himself in consequence facing two 

 alternatives, neither of which is he anxious 

 to accept. On the one side are the cham- 

 pions of chance; on the other, the apostles 

 of purpose. The issue may seem, to have 

 reduced itself to these alternatives. 



I beg your attention for a little while to 

 consider the import of this decision, and 

 I will take Bergson's view in his "L 'Evo- 

 lution Creatrice" as the clearest and most 

 profound expression of the hypothesis 

 that adaptation of the living world is the 

 outcome of a creative force that shapes 

 matter for an immediate purpose, though 

 not according to a preconceived or pre- 

 determined purpose. Many philosophers 

 have assumed a creative principle of some 

 kind that directs the organic world, but 

 have generally taken an anthropomorphic 

 conception of the process. Bergson, on the 

 other hand, conceives of creation without 



