260 PEESIDEXTIAL ADDRESS. 



faculties in man, and inherited epilepsy in guinea-pigs; 

 while Mr. Darwin cited the reduced wings of birds in 

 Oceanic islands, the drooping ears and deteriorated instinct 

 of domesticated animals, the diminished wing-power and en- 

 hanced leg-strength in domestic ducks, the short-sightedness 

 of civilized folk, the large hands of labourers' children, and 

 the thickened sole in infants and even embryos. 



This evidence has lately been carefully considered and 

 rigidty criticised by Mr. Piatt Ball in a little w^ork, entitled, 

 Are the Effects of Use and Disuse Inherited ? Mr. Ball's 

 criticisms are by no means of uniform cogency, and are at 

 times decided^ weak. But he has done ^vell in emphasizing 

 the extreme difficulty of excluding the effects of selection 

 and elimination by breeders and under nature. In illustra- 

 tion of this we may take the following case. Sir J. Crighton 

 Browne has shown that in the wild duck the brain is nearly 

 twice as heavy in proportion to the body as it is in the com- 

 paratively imbecile domestic duck. At first sight this looks 

 like evidence of inherited effects of disuse. But it may 

 fairly be urged that, owing to its stupidity, this imbecile 

 may be more readily kept in domestication. Imbecility has 

 thus been a character steadily selected by breeders, and 

 has carried wdth it a reduction of brains. This may perhaps 

 sound a little far-fetched as a mode of accounting for a 

 reduction of nearly fifty per cent., but it emphasizes the 

 difficulty or impossibility of excluding artificial selection as 

 a factor in the observed modifications of domestic animals. 

 So, too, with regard to natural selection. When we are told 

 by Mr. Ball that " natural selection would favour thickened 

 soles for walking on, and might also promote an early 

 development which w^ould ensure their beiug ready in good 

 time for actual use," we may be tempted to question 

 whether a thicker or thinner sole to the foot is a character 



