Peoblems and Concepts oe Evolution 21 



possible resistance between it and the conditions under which it must live. 

 This is a specific set of reactions which every species must undergo, and I have 

 seen many interesting examples of it in the introduction of one race from one 

 habitat to another, in which the habitat was not sufficiently different to serve 

 as an inhibition to its existence there, but in which there were sufficient differ- 

 ences m the new habitat to bring about in the introduced race distinct adjust- 

 ments of the organism, not in its qualities, but in its attributes and conditions, 

 which may become definitely altered and thereby produce a new localized habi- 

 tudinal race. When an organism has passed through the processes of origina- 

 tion, has been tested as to its ability to survive, and has adjusted itself to the 

 location into which it is placed, it takes its place as a member of the community, 

 and, in as far as anything which it exhibits is concerned, it may have been in 

 that community for himdreds of thousands of generations, when, as a matter of 

 fact, it may have been there less than a half dozen. 



This brings us to an important point in all of these operations in evolution, 

 namely, that when there is change it is rapid ; that the processes of origin pro- 

 duce transmuted factors in the organism within one or two or at the most a few 

 generations, and that the product appears finished and complete in all its 

 characteristics in a single relatively short series of processes. This may not be 

 universally true, but in any event the changes which I have observed have 

 reached completion in a short time, and the questions of conservation are 

 decided at once. The organism with its system either can or can not survive 

 under the conditions in which it arose, and this in every instance is decided in 

 one or in the most two or three generations, and the operations of equilibration 

 are again rapidly brought to a stable condition, so that in a half dozen or a dozen 

 generations from the beginning of the process of change the organism, so far 

 as appearances are concerned, in its stability and in appearance, might have 

 existed in its habitat for ten thousands of years. 



Many of the previous conceptions, especially those of Darwin and neo- 

 Darwinian schools, demand long-continued, faltering operations with irregular, 

 haphazard reactions, when as a matter of fact in observed instances the opera- 

 tions and reactions are as rapid, as specific, and as complete within a short time 

 from their start as are the operations in physical phenomena. This must of 

 necessity be so, because in all these operations there are involved only the 

 physical component agents within and without the organism; its gametic 

 factors and the processes which we analyze and describe, which are nothing but 

 the interaction of these physical substances and relations in terms of physical 

 process ; and this is the reason, apparently, why the reactions which have been 

 witnessed in experimental evolution have given so radically different a view- 

 point with regard to evolution problems. This brings us to the last point of con- 

 sideration — the point towards which we have been moving for more than three 

 centuries — namely, the question of an adequate formulation and experimental 

 investigation of a factorial theory of organic evolution. 



FACTORIAL THEORY OF EVOLUTION. 



It is difficult to decide where the first ideas of a factorial theory of evolution 

 arose, but certainly we can follow the development of it for a long time. This 

 is common knowledge, and everyone knows how Mallet, and Maupertius more 

 than a cehtury ago, formulated factorial concepts of organic constitution and of 



