400 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



But as regards organisms, the conformity of their structure to the 

 conditions under which they live, their adaptation in other words, a 

 fact everywhere seen in nature and forcibly expressed by the structure 

 of organized beings, can not be explained, with the fine simplicity 

 which Lamarck imagined, by the direct action of the ambient medium 

 in modeling the organism, precisely because of the organism's own 

 activity. It seems rather that the organism when it varies reacts, in a 

 manner which is peculiar to it and which results from its constitution, 

 to the most varied factors which can attract it, and that it passes, either 

 continuously or discontinuously, through a series of forms tending 

 toward a fixed limit. Eimer has expressed this by the word " ortho- 

 genesis," and the idea is taking a larger and larger place in biology. 

 Thus a branch of ungulates sprung from some ancestor analogous to 

 Ph&nacodus has terminated in the horses ; thus from Palaeomastodon 

 has gradually come the elephant type. At present we have more and 

 more numerous examples of series of this kind. The environment 

 could at most have had only an indirect action on this unfolding pro- 

 cess, which is the essence of evolution, hurrying it or retarding it, or 

 perhaps accomplishing a certain amount of elimination. 



Under the influence of these conceptions we see reappearing, among 

 biologists who are firm supporters of evolution, conceptions that are 

 related to those which were brought up in opposition to Darwinism at 

 its origin. Thus Mr. D. Rosa has recently published, under the title 

 " Hologenesis " (Ologenesi, Nuova teoria dell' Evoluzione, etc., 

 Florence, 1917), a theory in which he practically returns to ideas 

 nearly related to those of Naegeli, and in which he attributes the 

 whole of evolution to the play of internal factors of the constitution 

 of organisms. 



If adaptation is not necessarily a direct and normal effect of the 

 action of the environment on organisms, we are led to conclude that 

 it results secondarily from the choice on the part of organisms of a 

 mode of life which is appropriate to their preexisting constitution. 

 This is called by Mr. Cuenot preadaptation. The idea, however, is 

 not new. Darwin had difficulty in understanding how selection had 

 been able to bring about the perfection of the tongue of the wood- 

 peckers, so marvelously adapted to searching for insects in the bark 

 of trees. But Buffon, one of the precursors of the transformist 

 ideas, when describing the habits of these birds, concluded, as Bate- 

 son reminds us : " Such is the narrow and rude instinct of a bird 

 limited to a life of hardship and difficulty. It has received from 

 nature organs and instruments appropriate to this destiny, or rather 

 it has this very destiny on account of the organs that it is born 

 with." Here the organ would create the function inversely to the 

 Lamarckian aphorism. 



