PARASITISM AND SYMBIOSIS IN THEIR RELA- 

 TION TO THE PROBLEM OF EVOLUTION. 1 



By Maueice Caulleky. 



[Translated, with permission, by Gerrit S. Miller, jr., from Revue Scientifique, 



1919, pp. 737-745.] 



Everyone is now clearly aware of the critical phase that the problem 

 of transformism is passing through, a phase which F. le Dantec 

 called attention to in 1909 in the title of one of his books : La Crise du 

 Transformisme. This crisis, although very real, is certainly nothing 

 more than a crisis of growth. For my part I shall not try to meet it, 

 as Le Dantec does, by the affirmation of an uncompromising La- 

 marckism. And I shall recognize that Lamarckism and Darwinism, 

 the great partially seen solutions of the problem, in which more than a 

 generation of naturalists had faith, are now insufficient, at least in 

 their orthodox form. All nature forces upon our minds, and the more 

 strongly the better it becomes known, the conviction that organisms 

 have evolved, that they have passed through many stages in order to 

 become the species of which we find the fossil remains or which are 

 now living before our eyes. But it must be recognized that we do not' 

 know at present what have been the essential factors of this evolution. 

 All attempts thus far made to prove in an exact manner by the experi- 

 mental method the real transformational power of natural selection 

 or of the inheritance of acquired characters have led to nothing but 

 very meager results. And in presence of these results the experimental 

 study of heredity and variation, pursued so actively and so fruitfully 

 since the beginning of the twentieth century, leads, at least tentatively, 

 to conclusions which do not harmonize very well with Darwinism and 

 Lamarckism. It is true that they themselves lead, at least in their 

 most extreme form, to strange paradoxes such as Bateson brought for- 

 ward in 1914. (Presidential address, British Association for the Ad- 

 vancement of Science, Australian meeting, 1914.) It is also true that 

 the hypotheses best established in science, such as universal gravita- 

 tion or the principles of electromagnetism, finally encounter in our 

 minds difficulties which temporarily hold us in check. 



1 This article was the inaugural lecture of a course which was given at the Sorbonne in 

 Paris, and which has since been published in extenso in a book, " Le Parasitisme et la 

 Symbiose " (Encyclopedic Scientifique, Doin, 6diteur), Paris, 1921. 



