THE LAMARCKIAN THEORY 245 



factors the precedence over predetermination can be 

 designated as Lamarckian. 



While the Lamarckians (Spencer for example) do 

 not deny the reality of natural selection, they en- 

 deavour to restrict its field of action, and to place on 

 a par with it, if not above it, other factors, known as 

 Lamarckian factors. 



In the questions relative to ontogenesis and heredity, 

 the Lamarckians reject the idea of exclusive predeter- 

 mination, that is, the idea that the fertilised ovum con- 

 tains all the characters of the future individual. 



Lamarckism rallies all the scientists who consider 

 predetermination as only of secondary importance and 

 seek the explanation of ontogenesis and heredity in 

 the internal and external conditions which affect the 

 ovum in the course of its development. Lamarckism 

 stands for epigenesis as against preformation. All 

 the observations and experiments made to demonstrate 

 the heredity of acquired characters (a capital question 

 in Lamarckism) and all the theoretical considerations 

 which explain the mechanism of heredity are inspired 

 by the Lamarckian spirit. We may say that all the 

 research work of experimental zoology, more and more 

 frequently undertaken in our days, the studies in bio- 

 mechanics, inaugurated by Roux, in experimental 

 parthenogenesis, in experimental teratogenesis, the va- 

 rious experiments on the influence of temperature and 

 light on the organism, are Lamarckian in spirit. All 



