ESSAYS ON EVOLUTION. 



481 



to me that stable pigments are far more necessary for the butterfly 

 exposed to the light of a tropical sun than for the moth flying in the 

 evening or at night. Hence a much higher level of stability would 

 be selected in the pigments of butterflies than in those of moths." * 

 This is a good illustration of the usual Darwinian argument : assuming 

 the necessity of the greater stability, it is theoretically accounted for by 

 selection ; but why assume (as natural selection does) that a great number 

 were destroyed which had not the stability ; whereas the sun itself might 

 be equally assumed to be the external cause by which all the butterflies 

 submitted to it acquired the necessary degree of stability ? This theory 

 requires no destruction of inadaptive individuals at all. 



Professor Poulton reminds us that the late Professor Max Miiller " spoke 

 of the necessity of examining and, as time passes by, re-examining the 

 meaning of words." t No words require the application of this advice 

 more than " Natural Selection." Fifty years have seen the phrase develop 

 into a far wider usage than the description given of it by Darwin could 

 warrant. As the book before us is practically based upon it, it will be 

 as well to re-read the locus classicus in Darwin's work : 



" Can it be thought improbable, seeing that variations useful to man 

 have undoubtedly occurred, that other variations useful in some way to 

 each being in the great and complex battle of life, should occur in the 

 course of many successive generations ? t If such do occur, can we doubt 

 (remembering that many more individuals are born than can possibly 

 survive) that individuals having any advantage, however slight, over 

 others, would have the best chance of surviving and of procreating their 

 kind ? On the other hand, we may feel sure that any variation in the 

 least degree injurious would be rigidly destroyed. This preservation 

 of favourable individual differences and variations, and the destruction 

 of those which are injurious, I have called Natural Selection, or the 

 survival of the fittest." § 



By "injurious " we elsewhere learn that Darwin meant "inadaptive," 

 and by favourable " adaptive." 



The reader cannot help observing the very hypothetical style of the 

 above paragraph ; moreover, we have Darwin's assurance that " Natural 

 Selection " is merely a metaphor, because " it implies only the preserva- 

 tion of such variations as arise and are beneficial to the being under its 

 conditions of life," so that "it may metaphorically be said that natural 

 selection is daily and hourly scrutinizing throughout the world the 

 slightest variations." || 



The few words I have italicized strike at the root of natural selection ; 

 for no one has ever recorded a single instance of a growing plant or animal 

 developing a new variation injurious to itself. What really happens 

 under "changed conditions of life " is either for all the individuals to 

 acquire " definite " adaptive variations, or simply to die. For natural 

 selection " indefinite " variations are required.; i.e. the mixture of good 

 and bad variations in different individuals. Unfortunately for his theory, 

 * hoc. cit. p. xlv. f hoc. cit. p. 46. 



% Darwin does not here say "how " ; but in his other work (An. and PI. under 

 Dom. ii. 271) he attributes variations to the direct action of changed conditions of 

 life. 



§ Origin, &c. 6th Ed. p. 63. || Origin, dc. p. 65. 



VOL. XXXIV. I 



