INADEQUACY OF NATURAL SELECTION, ETC. 653 



kind of movement conflicts with efficient locomotion. There is a 

 waste of muscular energy in making these lateral movements, 

 and they are at variance with the forward movement. We may 

 infer, then, that the developing man profited by throwing the 

 stress as much as possible on the inner sides of the feet ; and was 

 especially led to do this when going fast, which enabled him to 

 abridge the oscillations : as indeed we now see in a drunken 

 man. Thus there was thrown a continually increasing stress 

 upon the inner digits as they progressively developed from the 

 effects of use ; until now that the inner digits, so large compared 

 with the others, bear the greater part of the weight, and being 

 relatively near one another, render needless any marked sway- 

 ings from side to side. But what has meanwhile happened to the 

 outer digits ? Evidently as fast as the great toes have come 

 more and more into play and developed, the little toes have gone 

 more and more out of play and have been dwindling for how 

 long shall we say ? perhaps a hundred thousand years. 



So far, then, am I from feeling that Professor Weismann has 

 here raised a difficulty in the way of the doctrine 1 hold, that 

 I feel indebted to him for having drawn attention to a very 

 strong evidence in its support. This modification in the form of 

 the foot, which has occurred since arboreal habits have given 

 place to terrestrial habits, shows the effects of use and disuse 

 simultaneously. The inner digits have increased by use while 

 the outer digits have decreased by disuse. 



Saying that he will not " pause to refute other apparent 

 proofs of the transmission of acquired characters," Professor 

 Weismann proceeds to deal with the argument which, with 

 various illustrations, I have several times urged the argument 

 that the natural selection of fortuitously -arising variations cannot 

 account for the adjustment of co-operative parts. Very clearly 

 and very fairly he summarises this argument as used in The 

 Principles of Biology in 1864. Admitting that in this case there 

 are " enormous difficulties " in the way of any other interpreta- 

 tion than the inheritance of acquired characters, Professor 

 Weismann before proceeding to assault this " last bulwark of 

 the Lamarckian principle," premises that the inheritance of ac- 

 quired characters cannot be a cause of change because inactive 

 as well as active parts degenerate when they cease to be of use : 

 instancing the " skin and skin-armature of crabs and insects." 

 On this I may remark in the first place that an argument 

 derived from degeneracy of passive structures scarcely meets 

 the case of development of active structures ; and I may re- 

 mark in the second place that 1 have never dreamt of denying 

 the efficiency of natural selection as a cause of degeneracy in 



