114 
THE DESCENT OF MAN. 
Part L 
that changed conditions produce some effect* and occa- 
sionally a considerable effect* on organisms 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 favour of this 
conclusion ; and valid reasons may be urged on the 
other side* at least as far as the innumerable structures 
are concerned* which are adapted for special ends. 
There can* however* be no doubt that changed condi- 
tions induce an almost indefinite amount of fluctuating 
variability* by which the whole organisation is rendered 
in some degree plastic. 
In the United States* above 1*000*000 soldiers* who 
served in the late war* were measured, and the States 
in which they were born and reared recorded. 16 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 manner of life delays growth* as shewn “ by 
“ the great difference between the statures of soldiers and 
“ sailors at the ages of 17 and 18 years.” Mr. B. A. Gould 
endeavoured to ascertain the nature of the influences 
which thus act on stature ; but he arrived only at nega- 
tive results, namely* that they did not relate to climate* 
the elevation of the land* soil* nor even “ in any con- 
“ trolling degree ” to the abundance or need of the com- 
16 ‘ Investigations in Military and Anthrop. Statistics/ &c. 1869, by 
B. A. Gould, p. 93, 107, 126, 131, 134. 
