zoo THE FIRST PRINCIPLES OF HEREDITY 



requirements of the trainer, are, of course, inherited. The 

 further fact that a constant improvement in successive 

 generations takes place may just as easily be due to artificial 

 selection as to the effect of use-inheritance, for it is well 

 known that dog-fanciers breed only from their best dogs. 

 Indeed, this is the method employed by all breeders for the 

 improvement of their stock, which applies as much to 

 sporting qualities as to other points. 



There is another set of factors the effects usually 

 attributed to the influence of civilized life which are 

 believed to yield strong evidence for the positive school. 

 Thus, Spencer mentions the short-sightedness of the 

 studious townsman, especially German ; the small hands, 

 jaws, and teeth of modern man ; the thick sole of the feet, 

 which is already distinct in the new-born infant : all features, 

 evidently acquired as an outcome of modern life, and 

 certainly inherited. But here the same argument applies 

 as before. The characters are inherited, no doubt, but 

 are they acquired ? As present-day competition does not 

 depend so much on physical excellence of eye, hand, or jaw 

 as on intellectual qualities, the individuals with defective 

 eyes, smaller jaws, etc., would have as much chance of 

 surviving as their betters, which in itself would lead to a 

 greater number of progeny of that type. Or to put it 

 another way, germinal variations cropping up in that 

 direction, not being detrimental in the struggle for life, 

 would not as hitherto be weeded out any longer. A state 

 of " Panmixia " would ensue, as Weismann termed it. 

 Deterioration would set in and continue with the aid of 

 Germinal Selection (as we have learnt already), until, 

 overstepping the limit and becoming dangerous to the 

 individual, it was checked by Natural Selection. The 

 history of the little toe gives clear proof that this interpreta- 

 tion is the correct one. The dwindling of the little toe in 

 civilized man has been attributed to the wearing of boots ; 

 but since it has been found in tribes which go barefoot, it 

 can only be ascribed to a natural tendency of the little toe 



