604 APPENDIX B. 



finger-ends were covered with glove-tips, reducing their sensitive 

 ness from one-twelfth of an. inch between compass-points to one- 

 seventh, lost nothing appreciable of their quickness and goodness 

 in sewing. An experience of my own here comes in evidence. 

 Towards the close of my salmon-fishing davs I used to observe 

 what a bungler I had become in putting on and taking off arti 

 ficial flies. As the tactual discriminativeness of my finger-ends, 

 recently tested, comes up to the standard specified by Weber, it 

 is clear that this decrease of manipulative power, accompanying 

 increase of age, was due to decrease in the delicacy of muscular 

 co-ordination and sense of pressure not to decrease of tactual 

 discriminativeness. But not making much of these criticisms, let 

 us admit the conclusion that this high perceptive power possessed 

 by the forefinger-end may have arisen by survival of the fittest ; 

 and let us limit the argument to the other differences. 



How about the back of the trunk and its face ? Is any advan 

 tage derived from possession of greater tactual discriminativeness 

 by the last than the first ? The tip of the nose has more than 

 three times the power of distinguishing relative positions which 

 the lower part of the forehead has. Can this greater power be 

 shown to have any advantage ? The back of the hand has 

 scarcely more discriminative ability than the crown of the head, 

 and has only one-fourteenth of that which the finger-tip has. 

 Why is this ? Advantage might occasionally be derived if the 

 back of the hand could tell us more than it does about the shapes 

 of the surfaces touched. Why should the thigh near the knee be 

 twice as perceptive as the middle of the thigh ? And, last of all, 

 why should the middle of the forearm, middle of the thigh, 

 middle of the back of the neck, and middle of the back, all stand 

 on the lowest level, as having but one-thirtieth of the perceptive 

 power which the tip of the forefinger has ? To prove that these 

 differences have arisen by natural selection, it has to be shown 

 that such small variation in one of the parts as might occur in a 

 generation say one-tenth extra amount has yielded an appre 

 ciably greater power of self-preservation ; and that those inherit 

 ing it have continued to be so far advantaged as to multiply 

 more than those who, in other respects equal, were less endowed 

 with this trait. Does any one think he can show this ? 



But if this distribution of tactual perceptiveness cannot be 

 explained by survival of the fittest, how can it be explained ? 

 The reply is that, if there has been in operation a cause which it 

 is now the fashion among biologists to ignore or deny, these 

 various differences are at once accounted for. This cause is the 

 inheritance of acquired characters. As a preliminary to setting 

 forth the argument showing this, I have made some experiments. 



It is a current belief that the fingers of the blind, more prac- 



