ON THK GENETIC VIEW OF NATURE. 



343 



objects and processes. The general laws which obtain 

 in this great field, and which would correspond to 

 Newton's laws of motion the laws of variation and of 

 heredity have not yet been discovered ; but it is again 

 Darwin more than any other naturalist who has called 

 attention to these prime movers in the living universe. 

 He has pushed into the foreground the two great problems 

 of " variation " and " heredity." l 



1 Darwin in his subsequent writ- 

 ings urged another important prob- 

 lem, to which he had already in his 

 first and greatest work drawn pass- 

 ing attention. This is the agency 

 of "sexual selection." It occupies 

 by far the larger portion of his 

 third great work, which appeared 

 in 1871 with the title ' The Descent 

 of Man and Selection in Relation to 

 Sex.' In the introduction he says, 

 " During many years it has seemed 

 to me highly probable that sexual 

 selection has played an important 

 part in differentiating the races of 

 man ; but in my ' Origin of Species ' 

 I contented myself by merely allud- 

 ing to this belief. When I came 

 to apply this view to man, I found 

 it indispensable to treat the whole 

 subject in full detail. Professor 

 Haeckel is the sole author who, 

 since the publication of the ' Origin,' 

 has discussed in his various works, 

 in a very able manner, the subject 

 of sexual selection, and has seen its 

 full importance." The problem of 

 "sexual selection " is introduced in 

 the ' Origin ' (p. 87) in the following 

 words : " Inasmuch as peculiarities 

 often appear under domestication 

 in one sex, and become hereditarily 

 attached to that sex, the same fact 

 probably occurs under nature ; and 

 if so, natural selection will be able 

 to modify one sex in its functional 

 relations to the other sex, or in 

 relation to wholly different habits 

 of life in the two sexes, as is some- 



40. 



Unsolved 

 problems. 



times the case with insects. And 

 this leads me to say a few words 

 on what I call Sexual Selection. 

 This depends not on a struggle for 

 existence, but on a struggle be- 

 tween the males for possession of 

 the females : the result is not 

 death to the unsuccessful com- 

 petitor, but few or no offspring. 

 Sexual selection is thus less rigor- 

 ous than natural selection." A 

 great deal has been written about 

 sexual selection, and in general it 

 may be said that the question be- 

 longs to quite a different category 

 from that of natural selection. 

 Some of the foremost champions of 

 the latter doctrine, notably Mr 

 Wallace, reject sexual selection as 

 unnecessary in the whole scheme. 

 The characteristic feature of natural 

 selection is this, that it is a purely 

 automatic process, dependent on 

 overcrowding, whereas in sexual 

 selection it becomes much more 

 difficult to see how the process 

 works automatically. Nowadays 

 the question of natural selection 

 is hardly any longer doubtful ; it 

 is a fact. As to sexual selec- 

 tion, the statistical proofs that 

 there is a superabundance from 

 which to choose are still wanting. 

 To understand sexual selection, 

 or even to define it, we need 

 to form some conception of the 

 reason and origin of sexual differ- 

 entiation, and this cannot be ar- 

 rived at without a theory of life 



