960 ON FORM AND MECHANICAL EFFICIENCY [ch. 



wearing on rosy breast and crimson wings a garment of in- 

 visibility, fades away into the sky at dawn or sunset like a cloud 

 incarnadine*. 



To buttress the theory of natural selection the sa'me instances 

 of "adaptation" (and many more) are used, as in an earher but not 

 distant age testified to the wisdom of the Creator and revealed to 

 simple piety the immediate finger of God. In the words of a certain 

 learned theologian f, ''The free use of final causes to explain what 

 seems obscure was temptingly easy-. . . . Hence the finalist was often 

 the man who made a liberal use of the ignava ratio, or lazy argument: 

 when you failed to explain a thing by the ordinary process of 

 causahty, you could 'explain' it by reference to some purpose of 

 nature or of its Creator. This method lent itself with dangerous 

 facility to the well-meant endeavours of the older theologians to 

 expound and emphasise the beneficence of the divine purpose." 

 Mutatis mutandis, the passage carries its plain message to the 

 naturahst. 



The fate of such arguments or illustrations is always the same. 

 They attract and captivate for awhile; they go to the building of 

 a creed, which contemporary orthodoxy % defends under its severest 

 penalties: but the time comes when they lose their fascination, 

 they somehow cease to satisfy and to convince, their foundations 



* They are "wonderfully fitted for 'vanishment' against the flushed, rich- 

 coloured skies of early morning and evening. . .their chief feeding - times " ; and 

 "look like a real sunset or dawn, repeated on the opposite side of the heavens — 

 either east or west as the case may be" (Thayer, Concealing -coloration in the Animal 

 Kingdom, New York, 1909, pp. 154-155). This hypothesis, like the rest, is not 

 free from difficulty. Twilight is apt to be short in the homes of the flamingo; 

 moreover, Mr Abel Chapman watched them on the Guadalquivir feeding by day, as 

 I also have seen them at Walfisch Bay. 



f Principal Galloway, Philosophy of Religion, 1914, p. 344. 



J Professor D. M. S. Watson, addressing the British Association in 1929 on 

 Adaptation, parted company with what I had called contemporary orthodoxy in 

 1917. Speaking of such morphological differences as "have commonly been 

 assumed to be of an adaptive nature," he said: "That these structural diflferences 

 are adaptive is for the most part pure assumption. . . .There is no branch of zoology 

 in which assumption has played a greater part, or evidence a less part, than in 

 the study of such presumed adaptations. ' ' Hume, in his Dialogue concerning Natural 

 Religion, shewed similar caut-ion: "Steps of a stair are plainly constructed that human 

 legs may use them in mounting; and this inference is certain and infallible. Human 

 legs are also contrived for walking and mounting ; and this inference, I allow, is not 

 altogether so certain." 



