46 THE FOUR SEGREGATIVE PRINCIPLES. 
tions in the same direction),’’** which are gradually accumulated by 
selection. Another point presented by the same writers is the conti- 
nuity of tradition, secured by training, suggestion, and example on 
the part of the parents and imitation on the part of the young. The 
effects of tradition have also been very clearly illustrated by F. W. 
Headley in his recent book.f I quote a few sentences in which he 
summarizes the effects of accommodation and tradition: 
The result is that among the higher plastic classes of animals evolution proceeds 
more rapidly. But obviously the quickening up of evolution is not all. The 
individual gains in importance. He improves his powers, is able to face a change 
of environment that otherwise would have been fatal. He makes an environment 
for his young in which intelligence can be developed; he chooses the environment 
which they shall have when out of the nursery, and so decides to some extent what 
qualities shall be the winning qualities in life. In fact, he is beginning to take the 
helm and steer the species. Or we may put it in this way: When the individuals 
of one generation decide the environment in which the next shall grow up, selec- 
tion ceases to be purely natural; it is in part artificial.t 
These quotations are sufficient to show that there is increasing 
recognition of the fact that there may be changes in the organism 
that are not dependent on changes in the environment, and are there- 
fore not dependent on change in the form of the natural selection. In 
choosing terms for designating these processes I think we should care- 
fully follow Professor Baldwin’s suggestion ‘‘that selection in the 
Darwinian sense should be used only when the essential conditions 
of organic progress by survival are present, namely, variations and 
physical heredity.’’s 
In my own usage, selection has been applied only to processes secur- 
ing the survival of part of the variations of a race or species with the 
exclusion of other variations, and so influencing its powers of heredity ; 
and isolation has been limited to the prevention of free crossing be- 
tween co-existing groups. In order to do this, and at the same time 
clearly present the principles controlling the evolution of habitudes, it 
has been necessary to find two terms that might hold the same rela- 
tion to innovation and tradition that selection and isolation hold to 
variation and heredity. The best words I have found are election 
* See letter from J. Mark Baldwin in Nature for April 15, 1897; also the same in 
Science for April 23, 1897, on ‘’Organic Selection.’”’ In this letter will be found 
references to discussion on the subject during the previous year in various books 
and journals. 
+ Problems of Evolution, pp. 120-128. London, Buckworth & Co., 1900, and 
New York, Crowell & Co., 1901. 
t Problems of Evolution, p. 128. 
§ See Science May 8,1898. The same limitation is also advocated in his Social 
and Ethical Interpretations, Appendix B. 
