THE HEREDITARY BASIS 21 
the case might be different. The latter variety might not yield 
more than a fourth of the former in either of the fields. In this 
instance the choice of the best seed would be more important than 
the choice of the best field. 
When we compare the influence of heredity and environmert 
it is necessary to state what particular hereditary conditions we 
are comparing with what given range of environmental conditions. 
We then have a soluble problem, at least theoretically. We might 
make a rough estimate of the relative importance of the heredi- 
tary conditions that are commonly found within the limits of the 
species or variety with the conditions that are produced by the 
variations of environment to which the species is commonly ex- 
posed. Leaving out of account the variations in heredity that 
might occur and taking the average of such variations as are 
actually met with, and leaving out of account what environmental 
conditions might accomplish and considering in general only what 
is actually done, we may obtain results that can be compared. 
We might find our species to be remarkably uniform in its heredi- 
tary constitution, and that the bulk of the diversity within it 
could be attributed to the effect of external conditions. On 
the other hand, the species might possess much hereditary 
variability like the mixed breeds of many of our domestic plants 
and animals in which the differences of innate constitution 
are much more conspicuous than those produced by the 
environment. 
Homo sapiens, the species in which we are particularly inter- 
ested in the present connection, contains a high degree of heredi- 
tary diversity. Not only does each of the major divisions of the 
species (if we may be permitted to group all mankind into one 
species) contain numerous minor groups which are commonly 
further subdivided, but most peoples, especially among civilized 
nations, represent racial mixtures of many different stocks. A 
little observation of the multitudes we encounter in going along a 
street cannot fail to impress one with the heterogeneity of his 
fellow creatures, and it does not require extensive dealings with 
our kind to convince one that they are as diverse in mental 
