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SCIENCE 



[Vol. LVI, No. 1456 



wliolly impossible with my time limitations. 

 But that these reasons have been convincing lo 

 a great number of the most distinguished stu- 

 dents of biology in recent years is certain. 

 Because some of them have frankly given ex- 

 pression to their doubts, has led many well- 

 meaning, but wholly uninformed, and somewhat 

 unintelligent, persons to conclude that leading 

 biologists no longer "believe in evolution." 

 Nothing could be more hopelessly wrong than 

 this conclusion. Every biologist who has got 

 beyond a first elementary course in the subject 

 knows that organic evolution is an observed 

 and observable fact of nature, of something 

 like the same obviousness and certainty as the 

 fact that unsupported pieces of matter fall to 

 the earth. I suppose that no one, even a "Fun- 

 damentalist," would think of asking a, physicist 

 if he "believed in gravitation." It is equally 

 absurd to ask a biologist if he "believes in evo- 

 lution." But just as one may appropriately 

 discuss today the relative merits of Newton's 

 and Einstein's views as to certain phases of 

 the problems presented by the phenomenon of 

 gravitation, so may he with propriety debate 

 the significance of Darwin's theory of natural 

 selection as a causative agent in the pheno- 

 menon of organic evolution. 



It must seem to a young man or woman em- 

 barking now upon a career in biology that 

 the only thing in the subject of any particu- 

 lar importance is genetics. I wish to point 

 out, with a gravity as becoming as it is difficult 

 to maintain while emitting such a platitude, 

 that this is not true. There is a great deal in 

 biology about which we are abysmally ignorant 

 which partakes neither of chromosomes, nor 

 Mendelism, nor yet of "crossing-over." And, 

 if I mistake not, little light is likely to be shed 

 on these dark places by the just now so bril- 

 liantly flaring torches that I have mentioned. 

 The advancement of biology has at least one 

 point in common with another fascinating sub- 

 ject, the adornment of women. Both progress 

 evolutionally by a series of waves of fashion. 

 Just now genetics is the reigning mode in 

 biology. Nothing could be more charming, but 

 it is neither the only nor the final word in 

 charm. 



It is apparently hopeless to expect anything 



like a reasonably balanced development in bio- 

 logical research, and, in consequence, of teach- 

 ing. And perhaps if we had it we should all 

 be bored. But it can do no harm if we think 

 once in a while about some of the fundamental 

 problems of biology which practically no one is 

 even making an attempt to investigate experi- 

 mentally, and towards the solution of which we 

 are apparently making little progi'ess. Time 

 will not permit to say all that I should like to 

 on this point, but I feel that I must in some de- 

 gree indicate that what I have just said about 

 the inadequacy of genetics as at present pur- 

 sued, is not merely an idle gibe. To this end I 

 shall discuss briefly two matters, adaptation 

 and heredity. 



The really difficult problem of evolution is 

 adaptation. The original student of adaptation 

 as a biological problem was Lamarck. It was 

 the problem that lay behind and beneath all of 

 Darwin's work, and he was almost the last in- 

 vestigator who in any systematic way busied 

 himself with the problem. It seems to me 

 that there are only two later students of this 

 problem whose work is of very considerable im- 

 portance, Hans Driesch and Lawrence J. Hen- 

 derson. There is an objectively manifest 

 teleology in animate nature. No thoughtful 

 person can fail to be deeply impressed with 

 the ingenuity and beauty with which organisms 

 and their parts are adapted to the attainment 

 of certain ends beneficial to the individual and 

 the race. How came these adaptations about? 

 What is the explanation? In the principle of 

 natural selection Darwin put forward the fii'st 

 and, so far, the only mechanistic explanation 

 of adaptation, though to Hume not Darwin 

 should be given the credit of origination so far 

 as this particular phase of the problem is con- 

 cerned. It took away, if correct, at one stroke 

 any necessity for the operation of supernatural 

 causes in the explanation of the living world. 

 It was this aspect of Darwin's theory of natural 

 selection which disturbed thoughtful theo- 

 logians vastly more than the fact of evolution 

 itself, the descent of man from lower animals. 

 For it was and is always possible, even if not 

 plausible, to argue that the Creator chose to 

 work in an evolutionary manner in the build- 

 ing of the world. But a strictly mechanistic 



