PRINCIPLES INTENSIFYING SEGREGATION. 175 
causes already considered. Segregation is not simply the indepen- 
dent generation of different sections of a species, but the independent 
generation of sections that differ. Though indiscriminate isolation of 
‘a small section of a species may produce an initial difference, it is 
evident that the degrees of difference may be greater or less, and that 
whatever causes a greater difference in two sections that are prevented 
from intergenerating will also be a cause of increased segregation, and 
may be classed as a form of intensive segregation. 
It has been observed that some of the causes enumerated in this 
chapter are primarily separative, and that no one of those that are 
primarily segregative is at any one time segregative in regard to many 
classes of characters. As several forms of segregation may codperate 
in securing a given division of a species, and one form is superimposed 
upon another, the aggregate effect must be great; but we easily 
perceive that it may be indefinitely enhanced by causes producing 
‘ increased divergence in the segregated branches. ‘The causes which 
produce monotypic evolution when associated with intergeneration 
must be equally effective in producing polytypic evolution when asso- 
ciated with isolation whether in its separative or segregative forms. 
But the discussion of intensive segregation must be reserved for 
another occasion. 
A Lack in this First Classtfication of Segregative Principles.* 
The classification’ of segregative principles here given does not draw any clear 
distinction between those resting upon acquired characters and habitudes and 
those resting upon innate characters and aptitudes. For example, industrial 
segregation is defined as “‘Segregation arising from the activities by which the 
organism protects itself against adverse influences in the environment, or by 
which it finds and appropriates special resources in the environment.” Now it 
is manifest that in some cases the different methods of using the environment may 
be determined by acquired habitudes rather than by inherited aptitudes, and the 
demarcation thus produced will, in the first place, be habitudinal, though in the 
end it may result in racial demarcation. 
The interaction between the principles producing racial segregation and those 
producing habitudinal segregation is discussed in Chapter V (pp. 45-78). 
It should also be noted that since this paper was brought before the Linnean 
Society, isolation has come into general use for designating the prevention of free 
crossing, by which the demarcation of racial groups is determined. This leaves 
the term ‘‘segregation”’ more free to designate the combined action of the prin- 
ciples producing the demarcation of groups and of those producing the intensifi- 
cation of the characters of the separated groups. Partition and isolation pro- 
‘duce habitudinal and racial demarcation, while election and selection produce 
habitudinal:and racial intensification, and the combined action of the four 
principles produces segregation both racial and habitudinal. (For a fuller state- 
ment see Chapters V and VI.) 
“As this explanation does not occur in the original paper it is printed in 
different form. 
