252 MONTGOMERY. [VoL. XII. 
It is not my intention to review the many theories already 
advanced to explain the nature and origin of variation, which 
would be a task too extensive for the scope of my present 
article. There are two well-known theories, each of which has 
latterly been more or less modified in regard to the origin of 
variation : the first teaches that variation is caused more or less 
directly by the environment ; while, according to the second, 
variation is the result of an inherent tendency on the part of 
the organism to vary. Now, in regard to the last-named theory, 
it may be said with truth that, though much may be explained 
on the assumption of “inherent tendencies,” there is no empirical 
proof of the existence of such tendencies ; and further, variation 
is not explained by the assumption of an inherent tendency to 
vary, until the origin and nature of the inherent tendency itself 
be explained. Reference may also be made to the theory of 
Weismann, that variation has its origin in conjugation. My 
own theory, as will be seen in the following pages, inclines 
somewhat to the doctrine of the origin of variation as caused 
by the influence of the environment, but is a new departure 
from the Lamarckian theory, inasmuch as I consider variation 
to be possible only under a temporary state of independence 
of the several organs, when their complete correlation has 
been disturbed by a change in the environment. 
The recent admirable work of Bateson! has shown clearly 
the importance of a careful comparative study of the phenomena 
of variation, for the understanding of the problems of morphol- 
ogy. In his book he has treated principally of the phenomena 
of variation in their relation to certain laws of bilateral and 
radial symmetry ; but the problem of the origin of variation he 
dismisses by stating that “Inquiry into the causes of variation 
is as yet, in my judgment, premature” (p. 78). My reason for 
attempting the solution of a problem so intricate and difficult 
in its nature is the need of approaching the question from a 
new point of view; and in this attempted solution I have 
endeavored to keep within the line of facts as much as possible, 
and to avoid making unnecessary theoretical assumptions. 
1 Wm. Bateson: Materials for the Study of Variation, treated with especial 
regard to Discontinuity in the Origin of Species. London, 1894. 
