MANNER OF DEVELOPMENT. 69 



permitted to say, as some excuse, that I had two distinct 

 objects in view; firstly, to show that species had not been 

 separately created, and secondly, that natural selection had 

 been the chief agent of change, though largely aided by 

 the inherited effects of habit, and slightly by the direct 

 action of the surrounding conditions. I was not, however, 

 able to annul the influence of my former belief, then 

 almost universal, that each species had been purposely 

 created; and this led to my tacit assumption that every de- 

 tail of structure, excepting rudiments, was of some special, 

 though unrecognized, service. Any one with this assump- 

 tion in his mind would naturally extend too far the action 

 of natural selection, either during past or present times. 

 Some of those who admit the principle of evolution, but 

 reject natural selection, seem to forget, when criticising 

 my book, that I had the above two objects in view; hence, 

 if I have erred in giving to natural selection great power, 

 which I am very far from admitting, or in having exagger- 

 ated its power, which is in itself probable, I have at least, 

 as I hope, done good service in aiding to overthrow the 

 dogma of separate creations. 



It is, as I can now see, probable that all organic 

 beings, including man, possess peculiarities of structure, 

 which neither are now, nor were formerly of any service to 

 them, and which, therefore, are of no physiological im- 

 portance. We know not what produces the numberless 

 slight differences between the individuals of each species, 

 for reversion only carries the problem a few steps back- 

 ward, but each peculiarity must have had its efficient 

 cause. If these causes, whatever they may be, were to act 

 more uniformly and energetically during a lengthened 

 period (and against this no reason can be assigned), the re- 

 sult would probably be not a mere slight individual differ- 

 ence, but a well-marked and constant modification, though 

 one of no physiological importance. Changed structures, 

 which are in no way beneficial, cannot be kept uniform 

 through natural selection, though the injurious will be 

 thus eliminated. Uniformity of character would, however, 

 naturally follow from the assumed uniformity of the excit- 

 ing causes, and likewise from the free intercrossing of 

 many individuals. During successive periods, the same 

 organism might in this manner acquire successive modifi- 

 cations, which would be transmitted in a nearly uniform 



