558 



SCIENCE 



[N. 8. Vol. XLIII. No. 1112 



of evolution, and in his presidential ad- 

 dress at the meeting of the British Associa- 

 tion in Australia, in 1914, he goes so far as 

 to express the idea that evolution might be 

 considered as the progressive unrolling of 

 an initial complexity, containing, from the 

 first, within itself, all the scope, the diver- 

 sity and all the differentiation now pre- 

 sented by living beings. As Mr. Castle 

 cleverly expressed it, carrying the idea to 

 its logical issue, man might be regarded as 

 a simplified ameba, a conclusion which may 

 well give us pause. Here we clearly recog- 

 nize, on the other hand, modernized in 

 form, but identical in principle, the con- 

 ception of the "enboitement" of the germs, 

 and of preformation, ideas to which, as I 

 have reminded you, the eighteenth century 

 applied the name evolution. It is a con- 

 ception diametrically opposed to that of 

 the transformism of the nineteenth century. 



Mr. Lotzy, struck by the results of the 

 crossing of distinct species of Antirrhinum, 

 has reached in the last three years the con- 

 clusion that a species is fixed and that 

 crossing is the only source of production of 

 new forms. Hybridization among species, 

 when it yields fertile offspring, may, ac- 

 cording to him, give rise, all at once, to a 

 whole series of new forms, whose mutual 

 relations and differential characteristics 

 correspond exactly to what the natural spe- 

 cies show. 



However subversive and delusive ideas 

 of this kind, positive or negative, appear 

 to generations saturated with Lamarckism 

 and Darwinism, we muBt not lose sight of 

 the fact that they were formulated by emi- 

 nent biologists, and that they are the result 

 of long and minute experimental researches 

 and that many of the facts on which they 

 rest may be considered as firmly estab- 

 lished. 



But without thinking of rebelling against 

 the facts resulting from genetic studies, we 



may question, whether they have so general 

 a significance. I have already more than 

 once pointed out that the present aspect of 

 organic heredity does not oblige us to con- 

 clude that it has always been the same. We 

 may ask ourselves whether conditions, 

 which have not yet been realized in experi- 

 ment, do not either modify directly the 

 germinal substance itself, or the correlation 

 existing between the parts of the soma, 

 and indirectly through them the germinal 

 substance. The facts which the study of 

 internal secretions are just beginning to 

 reveal, perhaps indicate a possibility of this 

 kind. Even if we admit that evolution pro- 

 ceeds only discontinuously by mutations, 

 we still have to discover the mechanism of 

 the production of these mutations. In 

 short, we may believe that, with heredity 

 and variations acting as recent researches 

 have shown them to act, there are neverthe- 

 less conditions that are still unknown and 

 that they have been realized for each series 

 of organisms only at certain periods, as 

 seems to be suggested by paleontology, and 

 in which the constitution and properties of 

 hereditary substances are changeable. Of 

 course these are purely hypothetical con- 

 jectures, but such conjectures must be 

 made if we wish to reconcile two categories 

 of already acquired data which we are ob- 

 liged to recognize as facts. On the one 

 hand we have the results of modern genet- 

 ics which of themselves lead to conceptions 

 of fixity, and on the other hand, the mass 

 of morphological data which, considered 

 from a rational point of view, seem to me to 

 possess the value of stubborn facts in sup- 

 port of the transformist conception. I will 

 even go so far as to say in support of a 

 transformism more or less Lamarckian. 



It seemed to me necessary to devote the 

 first meeting of the course to this general 

 analysis of the conditions under which the 

 problem of transformism now presents 



