434 DARWINISM chap. 



exclusive and unmodified action are nowhere to be found in 

 nature. It may be allowed to rank as one of those " laAvs of 

 growth," of which so many have now been indicated, and 

 which were always recognised by Darwin as underlying all 

 variation ; but unless we bear in mind that its action must 

 always be subordinated to natural selection, and that it is 

 continually checked, or diverted, or even reversed by the 

 necessity of adaptation to the environment, we shall be liable 

 to fall into such glaring errors as the imputing to " ebbing 

 vitality " alone such a widespread phenomenon as the occur- 

 rence of spines and thorns, while ignoring altogether the 

 influence of the organic environment in their production.^ 



The sketch now given of the chief attempts that have been 

 made to prove that either the direct action of the environment 

 or certain fundamental laws of variation are independent causes 

 of modification of species, shows us that their authors have, 

 in every case, failed to establish their contention. Any direct 

 action of the environment, or any characters acquired by use 

 or disuse, can have no efiect whatever upon the race unless 

 they are inherited ; and that they are inherited in any case, 



■^ Tlie general arguments and olijections here set fortli will apply with equal 

 force to Professor G. Henslow's tlieory of the origin of the various forms 

 and structures of flowers as due to "the responsive actions of the jarotoi^lasm 

 in consequence of tlie irritations set up by the weights, jn-essures, thrusts, 

 tensions, etc., of the insect visitors " {The Origin of Floral Structures through 

 Insect and other Agencies, p. 340). On the assumption that acquired char- 

 acters are inherited, such irritations may have had something to do with 

 the initiation of variations and with the production of certain details of 

 structure, but they are clearly incompetent to have brought about the 

 more imjiortant structural and functional modifications of flowers. Such 

 are, the various adjustments of leugtli and position of the stamens to bring 

 the pollen to the insect and from the insect to the stigma ; the various 

 motions of stamens and styles at the right time and the right direction ; 

 the physiological adjustments bringing about fertility or sterility in hetero- 

 styled plants ; the traps, springs, and complex movements of various jiarts 

 of orchids ; and innumerable otlier remarkable pdienomena. 



For the explanation of these we have no resource but variation and selec- 

 tion, to the effects of which, acting alternately with regi-ession or degi'adation 

 as above explained (p. 328) must be imputed the development of the count- 

 less floral structures we now behold. Even the primitive flowers, whose 

 initiation may, jjerhaps, have been caused, or rendered possible, by the 

 irritation set np by insects' visits, must, from their very origin, have been 

 modified, in accordance with the supreme law of utility, by means of varia- 

 tion and sui'vival of the fittest. 



