1887-88.] Colouring Matters of Leaves and Flowers. 295 



Mr Grant Allen and Dr J. E. Taylor in Colour Sense, in 

 Colours of Floiocrs, and in The Origin of Colour in Flotvers, — 

 have too exclusively drawn attention to natural selection, 

 referring only very inadequately to any physiological reasons 

 for its appearance. 



Now it is particularly necessary at the present time for 

 us to refer to these physiological causes, but before treating 

 the subject with some detail from this standpoint, it will 

 perhaps be as well to quote from the writings of those who 

 call our attention mainly to the influence of selection, so that 

 we may see what is the effect of this great natural force, to 

 the universal working of which Darwin has pre-eminently 

 drawn our attention. 



We have not to consider from the Origin of Species, nor 

 from Animals and Plants under Domestication, that Darwin 

 held natural selection as accountable alone for most observed 

 variations ; indeed, in one passage he speaks of evidence 

 existing as to the presence of internal causes of variation 

 which were not clearly enough evident to him for formula- 

 tion; but often he uses expressions indicating that he believed 

 variation to be indefinite, produced seemingly spontaneously, 

 occurring as it were by chance. Indeed, it is evident that 

 he often so spoke of chance or unaccountable variation, 

 where nowadays with greater physiological knowledge we 

 see at once the result of definite and easily recognisable 

 life-processes. 



That we are thus in a better position than ever before to 

 deal with such variations as those of colour, is due also to 

 the fact that, just as immediately after the publication of the 

 Origin of Species biologists gave an almost disproportionate 

 amount of attention to the action of natural selection, so 

 with an opposite swing, as it were, of the pendulum, we are 

 now ready to criticise natural selection and pay more atten- 

 tion to environment and the nature of the organism. 



As a witness to the truth of this fact, we have Mr Herbert 

 Spencer's two articles on " Factors in Organic Evolution," 

 recently published. 



That attention was disproportionately given to natural 

 selection in the question of flower-colour is not wonderful, 

 when Darwin was able to state in his great work (to what 

 extent correctly we are now more able to judge), that " if 



