366 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1915. 



the present time few are misled. The student of genetics knows that 

 the time for the development of theory is not yet. He would rather 

 stick to the seed pan and the incubator. 



In face of what we now know of the distribution of variability 

 in nature the scope claimed for natural selection in determining the 

 fixity of species must be greatly reduced. The doctrine of the sur- 

 vival of the fittest is undeniable so long as it is applied to the organ- 

 ism as a whole, but to attempt by this principle to find value in all 

 definiteness of parts and functions, and in the name of science to see 

 fitness everywhere is mere eighteenth-century optimism. Yet it was 

 in application to the parts, to the details of specific difference, to the 

 spots on the peacock's tail, to the coloring of an orchid flower, and 

 hosts of such examples, that the potency of natural selection was 

 urged with the strongest emphasis. Shorn of these pretensions the 

 doctrine of the survival of favored races is a truism, helping scarcely 

 at all to account for the diversity of species. Tolerance plays almost 

 as considerable a part. By these admissions almost the last shred of 

 that teleological fustian with which Victorian philosophy loved to 

 clothe the theory of evolution is destroyed. Those who would pro- 

 claim that whatever is is right will be wise henceforth to base this 

 faith frankly on the impregnable rock of superstition and to abstain 

 from direct appeals to natural fact. 



My predecessor said last year that in physics the age is one of rapid 

 progress and profound skepticism. In at least as high a degree this is 

 true of biology, and as a chief characteristic of modern evolutionary 

 thought we must confess also to a deep but irksome humility in pres- 

 ence of great vital problems. Every theory of evolution must be such 

 as to accord with the facts of physics and chemistry, a primary neces- 

 sity to which our predecessors paid small heed. For them the un- 

 Iniown was a rich mine of possibilities on v/hich they could freely 

 draw. For us it is rather an impenetrable mountain out of which the 

 truth can be chipped in rare and isolated fragments. Of the physics 

 and chemistry of life we know next to nothing. Somehow the char- 

 acters of living things are bound up in properties of colloids, and are 

 largely determined by the chemical powers of enzymes, but the study 

 of these classes of matter has only just begun. Living things are 

 found by a simple experiment to have powers undreamt of, and who 

 knows what may be behind? 



Naturally we turn aside from generalities. It is no time to discuss 

 the origin of the mollusca or of dicotjdedons, while we are not even 

 sure how it came to pass that Primula obconica has in 25 years pro- 

 duced its abundant new forms almost under our eyes. Knowledge of 

 heredity has so reacted on our conceptions of variation that very 

 competent men are even denying that variation in the old sense is a 

 genuine occurrence at all. Variation is postulated as the basis of all 



