8co THE POPULAR SCIENCE MONTHLY. 



sonably assume that in the absence of some differentiating pro- 

 cess, all parts of the surface would have like powers of perceiving 

 relative positions. They can not have become widely unlike in 

 perceptiveness without some cause. And if the cause alleged is 

 natural selection, then it is necessary to show that the greater 

 degree of the power possessed by this part than by that, has not 

 only conduced to the maintenance of life, but has conduced so 

 much that an individual in whom a variation had produced better 

 adjustment to needs, thereby maintained life when some others 

 lost it ; and that among the descendants inheriting this variation, 

 there was a derived advantage such as enabled them to multiply 

 more than the descendants of individuals not possessing it. Can 

 this, or anything like this, be shown ? 



That the superior perceptiveness of the forefiriger-tip has thus 

 arisen, might be contended with some apparent reason. Such 

 perceptiveness is an important aid to manipulation, and may have 

 sometimes given a life-saving advantage. In making arrows or 

 fish-hooks, a savage possessing some extra amount of it may have 

 been thereby enabled to get food where another failed. In civil- 

 ized life, too, a seamstress with well-endowed finger-ends might 

 be expected to gain a better livelihood than one with finger-ends 

 which were obtuse ; though this advantage would not be so great 

 as appears. I have found that two ladies whose finger-ends were 

 covered with glove-tips, reducing their sensitiveness 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. Toward the 

 close of my salmon-fishing days, I used to observe what a bungler 

 I had become in putting on and taking off artificial 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 con- 

 clusion that this high perceptive power possessed by the fore- 

 finger-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 by 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. 



