196 The American Naturalist. [March, 
At all events, this involves the Lamarckian principle, with all its 
necessary bearings upon our opinions as to Environment, Variation, 
Selection, and Inheritance. If we adopt it,we must accept its full con- 
sequences. Taking Spencer’s definition of Life as the continuous ad- 
justment of internal relations to external relations, we must regard 
the race as in part the summation of these individual adjustments, in 
part as the summation, by Selection, of favorable fortuitous varia- 
tions. Environment must act directly in producing variations in 
the organism as a whole; directly also it must produce special 
variations wherever it induces changes of function. As these 
variations are in a degree transmitted, we will discover some of 
the laws of variation in the study of individual adaptation; varia- 
tions of this kind will be found in definite lines; indefinite varia- 
tions will also arise from the fortuitous combination of individual 
characters; the proximate causes of variation must be changing 
environment as well as the combination of diverse individual 
characters. Selection, so far as it is here involved, will be found 
to act mainly upon the ensemble of characters which have their 
origin in individual variation by the extinction of unadapted 
individuals and races, but its action upon fortuitous variations 
will be concomitant. Inheritance must bear the burden not only 
of ancestral and race characters, but must accumulate the modifi- 
cations of these characters which occur in individuals. 
Let us associate the opposite principle, that special individual 
variations are not transmitted, with the name of Weismann, for at 
a time when Lamarck’s principle was rising in favor’ he boldly 
opposed it zz toto. His doctrine of the continuity of the germ- 
plasma, and especially of the isolation of the germ-cells from 
influences which are exerted upon the body-cells, is a perfect and 
necessary complement ‘of the doctrine that Evolution has ad- 
vanced by pure Natural Selection; he carries these twin doctrines 
out to their legitimate conclusions. Recalling Spencer's definition 
and applying Weismann’s principle, we must regard the race not 
as the summation of individual adjustments, but as the summa- 
tion of the best adjusted germ-plasmata. Environment may act 
12 In 1883, when Weismann published his first essay on Heredity, the only English oF 
American it it woke ES r af the Lamarckian prin- 
ciple was Alfred Wallace, 
