208 



SCIENCE 



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



tion. that imless vce can find sncli a rela- 

 tion, the whole fabric of natural selection 

 falls to the gronnd ; and. as is well known, 

 he attempted to supply this deficiency in 

 his competition of the biophors in the 

 germ-cells. His attempt has failed, on 

 the whole, to bring conviction that the re- 

 sult has been reached in this way, biit his 

 statement, in regard to the weakness of 

 the appeal to chance, has, I believe, struck 

 a responsive cord. 



It seems to me that we get a suggestion 

 of how continiious adjustment is more 

 likely to occur if we refer variations not 

 to internal conflicts of the biophoi-s, but to 

 the action of external factors on the genu 

 plasm, and assume that germinal material 

 that shows itself susceptible of change in 

 an environment is more likely to show 

 further variations in the same direction in 

 that environment. 



On some such view we can better under- 

 stand how evolution along adaptive lines 

 is more likely to give further variations in 

 the same direction, and there is not a little 

 evidence in favor of this view in the his- 

 tory of domesticated animals and plants. 

 After the first step, which was undirected, 

 i. e., not purposeful, the subsequent events 

 are rendered more probable; for the dice 

 are loaded. Evolution along adaptive 

 lines would be a consequence of the very 

 processes that variation has initiated. 



The same idea shows how incipient 

 stages of organs may progress until they 

 become of positive advantage to the race 

 and may ultimately carry it along a pro- 

 gressive line of evolution: or should the 

 variation be baleful, lead in its ultimate 

 development to the destruction of the 

 species. 



Turning now to another aspect of the 

 siibject, I think that oiir ideas concerning 

 chance and purpose have been largely in- 

 fluenced by those creative processes in 



which man himself seems to have played 

 a leading role. I refer to the artificial 

 production of our domesticated animals 

 and cultivated plants. 



"We owe to Darwin chiefly a comparison 

 between certain features in the develop- 

 ment of adaptation i;nder domestication 

 and the development of adaptation in na- 

 tiire. 



Domesticated hens lay more eggs than 

 Gallus hal-kiva. Cows give more milk 

 than bufl:'aloes. Apples in an orchard are 

 larger than in the forest. Potatoes are 

 bigger in a garden than in the wilds of 

 Chili. TVhy" lu part, no doubt, because 

 better conditions of soil or of feeding keep 

 i;p the product to its maximum, but no 

 one wiU claim for a moment that the only 

 dift'erence is in the better conditions of 

 food. We realize that the results have not 

 and could not have been obtained from the 

 wild fox'ms at once, but only through a 

 long process of artificial selection by 

 which the domesticated animals have be- 

 come adeipted to man's needs. 



Admitting this, as one must, what is its 

 bearing on our problem? It is admitted 

 that artificial selection has created noth- 

 ing new, it has supplied only an oppor- 

 tunity for what already appeared, as new, 

 to remain in existence, but, by picking out 

 the new variation and isolating it under 

 conditions where it can live, purpose enters 

 in as a factor, for selection had an end in 

 view. 



By preserving the variation the possi- 

 bility of further variation in the same 

 direction is insured. 



"We see clearly enough the role that 

 chance and purpose play in these proc- 

 esses. The first variation is the result of 

 the environment acting on the organism; 

 it happened, "chanced," to appear at a 

 time when a man was there to give it an 

 opportunity to live. And aboi;t its pur- 



