Chap. IT.] MANNER OF DEVELOPMENT. 147 



aided by the inherited effects of habit, and slightly by the 

 direct action of the surrounding conditions. Nevertheless 

 I was not able to annul the influence of my former belief, 

 then widely prevalent, that each species had been pur- 

 posely created; and this led to my tacitly assuming that 

 every detail of structure, excepting rudiments, was of 

 some special, though unrecognized, service. Any one 

 with this assumption in his mind would naturally extend 

 the action of natural selection, either during past or pres- 

 ent times, too far. Some of those who admit the principle 

 of evolution, but reject natural selection, seem to forget, 

 when criticising mv book, that I had the above two ob- 

 jects in view ; hence if I have erred in giving to natural 

 selection great power, which I am far from admitting, or 

 in having exaggerated its power, which is in itself prob- 

 able, I have at least, as I hope, done good service in aid- 

 ing to overthrow the dogma of separate creations. 



That all organic beings, including man, present many 

 modifications of structure which are of no service to them 

 at present, nor have been formerly, is, as I can now see, 

 probable. 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 own efficient 

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

 act more uniformly and energetically during a lengthened 

 period (and no reason can be assigned why this should not 

 sometimes occur), the result would probably be not mere 

 slight individual differences, but well-marked, constant 

 modifications. Modifications which are in no way bene- 

 ficial cannot have been kept uniform through natural se- 

 lection, though any which were injurious would have been 

 thus eliminated. Uniformity of character would, how- 

 ever, naturally follow from the assumed uniformity of the 

 exciting causes, and likewise from the free intercrossing 



