MANNER OF DEVELOPMENT. 59 



now appear to us useless, will hereafter be proved to be use- 

 ful, and will therefore come within the range of natural selection. 

 Nevertheless, I did not formerly consider sufficiently the existence 

 of structures, which, as far as we can at present judge, are neither 

 beneficial nor injurious; and this I believe to be one of the greatest 

 oversights as yet detected in my work. I may be 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 uni- 

 versal, that each species had been purposely created; and this led 

 to my tacit assumption that every detail of structure, excepting 

 rudiments, was of some special, though unrecognized, service. 

 Any one with this assumption in his mine', would naturally ex- 

 tend too far the action of natural selection, either during past or 

 present times. Some of those who admit the principle of evolu- 

 tion, but reject natural selection, seem to forget, when criticizing 

 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 exaggerated 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, includ- 

 ing man, possess peculiarities of structure, which neither are now, 

 nor were formerly of any service to them, and which, therefore, 

 are of no physiological importance. 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- 

 wards; 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 result would probably be not a mere 

 slight individual difference, but a well-marked and constant modi- 

 fication, 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 elimi- 

 nated. Uniformity of character would, however, naturally follow 

 from the assumed uniformity of the exciting causes, and likewise 

 from the free intercrossing of many individuals. During- succes- 

 sive periods, the same organism might in this manner acquire 

 successive modifications, which would be transmitted in a nearly 

 uniform state as long as the exciting causes remained the same 

 and there was free intercrossing. With respect to the exciting 

 causes we can only say, as when speaking of so-called spontaneous 

 variations, that they relate much more closely to the constitution 



