REGENERATION AND LIABILITY TO INJURY 109 



about this supposed process, we shall find ample grounds for doubt, 

 and even, I think, for denial that the results could ever have been 

 brought about in this way. 



In the first place, the assumption that the regeneration of an 

 organ can be accounted for as a result of the selection of those indi- 

 vidual variations that are somewhat more perfect, rests on the 

 ground that such variations occur, for the injury itself that acts as a 

 stimulus is not supposed to have any direct influence on the result, 

 i.e. for better or worse. All that natural selection pretends to do is 

 to build up the complete power of regeneration by selecting the most 

 successful results in the right direction. In the end this really goes 

 back to the assumption that the tissue in itself has power to regen- 

 erate more completely in some individuals than in others. It is just 

 this difference, if it could be shown to exist, that is the scientific 

 problem. But, even leaving this criticism to one side, since it is very 

 generally admitted, it will be clear that in many cases most of the 

 less complete stages of regeneration that are assumed to occur in the 

 phyletic series could be, in each case, of very little use to the indi- 

 vidual. It is only the completed organ that can be used ; hence the 

 very basis of the argument falls to the ground. The building up of 

 the complete regeneration by slowly acquired steps, that cannot be 

 decisive in the battle for existence, is not a process that can be 

 explained by the theory. 



There is another consideration that is equally important. It is 

 assumed that those individuals that regenerate better than those that 

 do not, survive, or at least have more descendants ; but it should not 

 be overlooked that the individuals that are not injured (and they will 

 belong to both of the above classes) are in even a better position than 

 are those that have been injured and have only incompletely regen- 

 erated. The uninjured forms, even if they did not crowd out the 

 regenerating ones, which they should do on the hypothesis, would 

 still intercross with them, and in so doing bring back to the average 

 the ability of the organism to regenerate. Here we touch upon a 

 fatal objection to the theory of natural selection that Darwin himself 

 came to recognize in the later editions of the Origin of Species, 

 namely, that unless a considerable number of individuals in each gen- 

 eration show the same variation, the result will be lost by the swamping 

 effects of intercrossing. If this be granted, there is left very little 

 for selection to do except to weed out a few unsuccessful competitors, 

 and if the same causes that gave origin to the new variation on a 

 large scale should continue to act, it will by itself bring about the 

 result, and it seems hardly necessary to call in another and question- 

 able hypothesis. 



Finally, a further objection may be stated that in itself is fatal to 



