PROBLEM OF EVOLUTION CAULLERY. 327 



external contingencies. Between such views there is in reality no 

 considerable difference. Such an idea substitutes for successive 

 creations one initial creation with successive and continuing mani- 

 festations. The present crisis of transformism, as Le Dantec and 

 others set it forth, is the conflict concerning the reciprocal value 

 of external and internal factors in evolution. 



The two j)rincipal and classic solutions proposed to explain evo- 

 lution were based on the efficacy of external factors, both the theory 

 advanced by Lamarck in 1809 in his Philosophie Zoologique, as 

 well as that of Darwin, formulated in 1859, in The Origin of Spe- 

 cies. Lamarck starts in fact with the statement that the structure 

 of organisms is in harmony with the conditions under which they 

 live and that it is adapted to these conditions. This adaptation is, 

 in his opinion, not an a priori fact, but a result. The organism is 

 shaped by the environment; usage develops the organs in the indi- 

 vidual; without usage they become atrophied. The modifications 

 thus acquired are transmitted to posterity. Adaptation of indi- 

 viduals, inheritance of acquired characteristics — ^these are the funda- 

 mental principles of Lamarckism. Except for its verification, it is 

 the most complete scientific theory of transformism which has been 

 formulated, because it looks to the very cause of the change of or- 

 ganisms by its method of explaining adaptation. Darwin adopted 

 the idea of Lamarck and admitted theoretically adaptation and the 

 inheritance of acquired characteristics, but he accorded to them only 

 a secondary importance in the accomplishment of evolution. The 

 basis for him is the variability of organisms, a general characteristic 

 whose mechanism he did not try to determine and which he accepts 

 as a fact. This being so, the essential factor of the gradual trans- 

 formation of species is the struggle for life between the individuals 

 within each species and between the different species. The individ- 

 uals which present advantageous variations under the conditions in 

 which they live have more chance to survive and to reproduce them- 

 selves; those which, on the contrary, offer disadvantageous variations 

 run more chance of being suppressed without reproducing them- 

 selves. There is established, then, automatically a choice between in- 

 dividuals, or, according to the accepted terminology, a natural selec- 

 tion^ a choice which perpetuates the advantageous variations and 

 eliminates the others. And with this going on in each generation the 

 type is transformed little by little. Natural selection accumulates 

 the results of variation. 



This is not the time to discuss Darwin's theory. I wish only to 

 observe at this time that it is less complete than that of Lamarck in 

 that it does not try to discover the cause of variations ; also that, like 

 that of Lamarck, it attributes a considerable participation to the con- 



