424 The American Naturalist. [May, 
our reach admitting such exact analysis of variation in the 
planes of time and fitness. When, again, we connect human 
anatomy as a field for the study of Variation with Galton’s 
researches, although his emphasis has been chiefly upon the 
laws of Repetition, we begin to appreciate the far-reaching 
importance of his inductions. In contrast with those of Weis- 
mann they are based upon facts and will stand. In the first 
volume of these Marine Biological Laboratory lectures I went 
into some detail to show how Galton bears upon the modern 
evolution problem, so that here I may briefly recapitulate. He 
demonstrates two principles: First, that there must be some 
strong progressive variational tendency in organisms to offset 
the strongly retrogressive principle of Repetition wherever 
the neutralizing or swamping effect of natural inter-breeding 
is in force, as it virtually is for most anatomical characters of 
the human race. Second, he shows what has not been pointed 
out in this connection before, that in natural inter-breeding 
ontogenic or individual variations are conspicuous but in the 
main temporary, while there is a strong undercurrent of phylo- 
genic variations relatively inconspicuous and permanent. 
Other evidence supporting this latter principle comes out as we 
proceed. 
What is the value of a distinction between ontogenic and 
phylogenic variations? It is this: it sets forth the widely 
neglected initial problem of the time of origin of a variation 
in the life history of the individual. This is the first step in 
experimentation upon variation, not only as it will afford 
crucial evidence as to the factors of Buffon, Lamarck, and of 
St. Hilaire, which hinge upon the inheritance of acquired varia- 
tions, but in the coming days of exact research upon Variation 
in general. Let ontogenic variation—a term first used by 
Brooks, I believe, although I cannot point out where—include 
all deviations from type which have their cause in any stage 
of individual development. We are now beginning to fully 
recognize that the causes of certain kinds of variation actually 
can be traced to external influences upon certain stages of 
growth or ontogeny, and that it will be possible ultimately to 
determine these stages when this matter of time is established 
