April 21, 1916] 



SCIENCE 



557 



such and such properties in a single indi- 

 vidual, or on the contrary we can separate 

 them. The biologist deals with these unit 

 characteristics as the chemist does with 

 atoms, or with lateral chains, in a complex 

 organic compound. The properties which 

 we distinguish thus are nothing but the 

 very indirect external expression of consti- 

 tuent characteristics of the fundamental 

 living substance of the species. But we 

 imagine, and it is in this that the enormous 

 importance of Mendelism consists, that it 

 has been the means of giving us a more pre- 

 cise idea than we have had heretofore of 

 a substantial basis for heredity. In itself, 

 Mendelism is only symbolism, like the 

 atomic theory in chemistry, but the case of 

 chemistry shows what can be drawn from a 

 well conceived symbolism and the Men- 

 delian symbolism becomes more perfect 

 each day in its form, in its conception and 

 in its application. The recent works of 

 T. H. Morgan^ are particularly interesting 

 in this respect. 



Further, the facts furnished by Mendel- 

 ism agree well with those of cytology. The 

 results are explained easily enough, if we 

 accord to the chromatine in the nucleus and 

 particularly to chromosomes, a special value 

 in heredity. The agreement of cytology 

 and of Mendelism is incontestably a very 

 convincing fact and a guide in present 

 research. 



But if we return now to the study of 

 evolution, the data of Mendelism embarrass 

 us also very considerably. All that it shows 

 us in fact is the conservation of existing 

 properties. Many variations which might 

 have seemed to be new properties are simply 

 traced to previously unobserved combina- 

 tions of factors already existing. This has 

 indeed seriously impaired the mutation 



6 Cf. Morgan, Sturtevant, Muller and Bridges, 

 "The Mechanism of Mendelian Heredity," New 

 York, 1915. 



theory of De Vries, the fundamental ex- 

 ample of the CEnothera lamarckiana seem- 

 ing to be not a special type of variation, but 

 an example of complex hybridization. The 

 authors who have especially studied Men- 

 delian heredity find themselves obliged to 

 attribute all the observed facts to combina- 

 tions of already existing factors, or to the 

 loss of factors, a conception which seems 

 to me a natural consequence of the symbol- 

 ism adopted, but which hardly satisfies the 

 intelligence. In any case, we do not see in 

 the facts emerging from the study of Men- 

 delism, how evolution, in the sense that mor- 

 phology suggests, can have come about. 

 And it comes to pass that some of the biol- 

 ogists of greatest authority in the study of 

 Mendelian heredity are led, with regard to 

 evolution, either to more or less complete 

 agnosticism, or to the expression of ideas 

 quite opposed to those of the preceding gen- 

 eration; ideas which would almost take us 

 back to creationism. 



Lamarckism and Darwinism are equally 

 affected by these views. The inheritance of 

 acquired characters is condemned and nat- 

 ural selection declared unable to produce a 

 lasting and progressive change in organ- 

 isms. The facts of adaptation are explained 

 by a previous realization of structures 

 which are found secondarily in harmony 

 with varied surroundings. That is the idea 

 which different biologists have reached and 

 which M. Cuenot in particular has devel- 

 oped systematically.® 



Two recent and particularly significant 

 examples of these two tendencies are fur- 

 nished us by W. Bateson and by J. P. 

 Lotzy. In his "Problems of Genetics," 

 Bateson declares that we must recognize 

 our almost entire ignorance of the processes 



6 Cuenot, ' ' La Genfese des esp6ces animales, ' ' 

 Paris, BibliothSque Soientifique Internationale 

 (Alcan), 1911. — "ThSorie de la preadaptation," 

 Scientia, Tome 16, p. 60, 1914. 



