336 THE STRUCTURE OF FLOWERS. 



of flowers ; whereas " natural selection " leaves us exactly 

 where we were before. Moreover, natural selection is made 

 to cover exactly opposite processes ; for the formation of the 

 enlarged lip, on the one hand, would be attributed to it, just 

 as much as the elimination of a stamen altogether, on the 

 other. Instead, therefore, of using this term as the cause of 

 anything and everything, I prefer to attribute effects to 

 hypertrophy, atrophy, resistance to strains, responsive action 

 to irritations, and so on. If it be thought that natural selec- 

 tion somehow underlies all this, the reader is at liberty 

 to substitute the phrase; but, I must confess, it conveys 

 nothing definite to my mind, while the others undoubtedly do. 

 I do not wish the reader to suppose that my theory is 

 altogether in opposition to Mr. Darwin's ; for it must not be 

 forgotten that he himself laid great stress on the environ- 

 ment as a cause of variability upon which, when once brought 

 about, natural selection could then act. Thus he remarks : 

 " To sum up on the origin of our domestic races of animals 

 and plants. Changed conditions of life are of the highest 

 importance in causing variability, both by acting directly on 

 the organisation, and indirectly by affecting the reproductive 

 system. It is not probable that variability is an inherent 

 and necessary contingent, under all circumstances. . . . Vari- 

 ability is governed by many unknown laws, of which corre- 

 lated growth is probably the most important. Something, 

 but how much we do not know, may be attributed to the 

 definite action of the conditions of life. [Under this I would 

 include the definite action of insects exerted mechanically 

 upon the organs of flowers.] Some, perhaps a great, effect 

 may be attributed to the increased use or disuse of parts. 

 [Compensation plays undoubtedly a very important part]. . . 

 Over all these causes of Change, the accumulative action 

 of Selection, whether applied methodically and quickly, or 



