1897.] The Limits of Organic Selection. 945 
from ancestral types which have become permanently estab- 
lished. They constitute the main evidence for determinate 
variation and as a consequence determinate evolution. 
In every analysis of variation these distinctions are of pro- 
found importance, because every adult organ we study 
(whether with Weldon it is the frontal measurement of a crab 
or, with Cope and Tornier, the articular facet of a bone), may 
be an exponent either of constitutional, phylogenic, or stirp 
factors, or of new environmental and ontogenic factors, or of 
the fortuitous or chance elements in development, or finally 
of all three factors combined. 
In March, 1896, the application of this distinction to the 
problem of the causes of “ determinate variation” was pointed 
out by myself in course of a discussion in the New York Acad- 
emy of Sciences (p. 141) as follows: “ For example, if the hu- 
man infant were brought up in the branches of a tree as an 
arboreal type instead of asa terrestrial, bi-pedal type, there is 
little doubt that some of the well known early adaptations to 
arboreal habit (such as the turning in of the soles of the feet, and 
the grasping of the hands) might be retained and cultivated ; 
thus a profoundly different type of man would be produced. 
Similar cl) oges in the action of environment are constantly 
in progres: in nature, since there is no doubt that the changes 
of environment and the habits which it so brings about far 
outstrip all changes in constitution. During the enormously — 
long period of time in which habits induce ontogenic varia- 
tions, it is possible for natural selection to work very slowly 
and gradually upon predispositions to useful correlated varia- 
tions, and thus what are primarily ontogenic variations become 
slowly apparent as phylogenic variations or congenital charac- 
ters of the race. Man, for instance, has been upon the earth 
perhaps seventy thousand years; natural selection has been 
slowly operating upon certain of these predispositions, but has 
not yet eliminated those traces of the human arboreal habits, 
nor completely adapted the human frame to the upright posi- 
tion. Thisis as much an expression of habit and ontogenic 
variation as it is a constitutional character. This fact, which 
has not been sufficiently emphasized before, offers an explana- 
