DESCENT OF MAN FROM SOME LOWER FORM. 155 



Not only does variability appear to be induced in man 

 and the lower animals by the same general causes, but in 

 both the same parts of the body are affected in a closely 

 analogous manner. 



ACTION OF CHANGED CONDITIONS. 



This is a most perplexing subject. It can 

 not be denied that changed conditions pro- 

 duce some, and occasionally a considerable, effect on or- 

 ganisms of all kinds ; and it seems at first probable that 

 if sufficient time were allowed this would be the invariable 

 result. But I have failed to obtain clear evidence in favor 

 of this conclusion ; and valid reasons may be urged on 

 the other side, at least as far as the innumerable struct- 

 ures are concerned, which are adapted for special ends. 

 There can, however, be no doubt that changed conditions 

 induce an almost indefinite amount of fluctuating varia- 

 bility, by which the whole organization is rendered in 

 some degree plastic. 



In the United States, above one million soldiers, 

 who served in the late war, were measured, and the States 

 in which they were born and reared were recorded. 

 From this astonishing number of observations it is 

 proved that local influences of some kind act directly on 

 stature ; and we further learn that " the State where 

 the physical growth has in great measure taken place, and 

 the State of birth, which indicates the ancestry, seem to 

 exert a marked influence on the stature." For instance, 

 it is established that "residence in the "Western States, 

 during the years of growth, tends to produce increase of 

 stature." On the other hand, it is certain that, with 

 sailors, their life delays growth, as shown " by the great 



'erence between the statures of soldiers and sailors at 



diff 



