THE UNKNOWN FACTORS OF EVOLUTION. 85 



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 vari- 

 ations, 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 ^xternal 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 



