58 THE FOUR SEGREGATIVE PRINCIPLES. 
new forms of partition open the way for diverse forms of election, 
which result in the success of divergent habitudes in the sepa- 
rated groups; and these divergent habitudes may bring the individ- 
uals to whom they belong into positions producing isolation, and into 
divergent methods of dealing with the environment, and so subject 
them to divergent forms of selection producing divergent racial evo- 
lution. 
We therefore observe that, in the evolution of the higher types of 
animals, each of these four principles must have a most important 
part; for, in producing divergent racial types, isolation is absolutely 
essential, and partition is the forerunner preparing the way for isola- 
tion. Again, selection usually operates in each generation, either in 
giving emphasis and stability to types already attained, or in mold- 
ing the separate groups created by partition and isolation, according 
to new necessities, which are, in most cases, introduced by the new 
experiments, new attainments, and new habitudes that have been 
established by the different forms of election. My interpretation of 
these factors does not tend toward the minimizing of the importance 
of selection; but it shows that isolation, partition, and election are of 
equal importance in their ownspheres. It shows that the transfor- 
mation of forms that do not freely intergenerate is always more or less 
divergent, and that the racial divergence of any two forms is absolutely 
dependent on isolation, 2. e , the prevention of free crossing. It fur- 
ther emphasizes the fact that selection, both in its reflexive and its 
environal forms, is in a large degree controlled by the varying habi- 
tudes and aptitudes of different sections of a species, so that the iso- 
lated portions of a variable species would in time develop different 
forms of selection, even if they could be exposed to absolutely similar 
environments. These points are all presented in full in the paper 
reproduced in Appendix II, but the new nomenclature here introduced 
facilitates our apprehension of the facts. 
3. The Two Methods of Generalization. 
Racial generalization is produced by heredity with free crossing 
within the bounds of each racial group. Habitudinal generalization 
is produced by tradition with free association within the bounds of the 
social group. The influence of heredity is so fully recognized that we 
need not stop to illustrate the fact that two or more somewhat diver- 
gent types, when freely intergenerating for many generations, will be 
reduced to a single racial (or aptitudinal) type which is perpetuated 
with considerable constancy from generation to generation. It is also 
manifest that tradition, which transmits the habits of each generation 
to the next, through the training and suggestion given by parents to 
