No. 531] GENOTYPE CONCEPTION OF HEREDITY 131 



The main result of all true analytical experiments in 

 questions concerning genetics is the upsetting of the 

 transmission-conception of heredity, and the two differ- 

 ent ways of genetic research: pure line breeding as well 

 as hybridization after Mendel's model, have in that 

 respect led to the same point of view, the "genotype- 

 conception" as we may call the conception of heredity 

 just now sketched. 



Here we can not trace the historical evolution of the 

 ideas concerning heredity, not even in the last ten years, 

 but it must be stated as a fact that a very great number of 

 the terms used by the modern biological writers have been 

 created under the auspices of the transmission-concep- 

 tion, and that perhaps the greater number of botanists 

 and zoologists are not yet emancipated from that old con- 

 ception. Even convinced Mendelians may occasionally 

 be caught using such words as " transmission" and other 

 now obsolete terms. 



The science of genetics is in a transition period, becom- 

 ing an exact science just as the chemistry in the times of 

 Lavoisier, who made the balance an indispensable imple- 

 ment in chemical research. 



The "genotype-conception," as I have called the 

 modern view of heredity, differs not only from the old 

 "transmission-conception" as above mentioned, but it 

 differs also from the related hypothetical views of Gralton, 

 Weismann and others, who with more or less effectiveness 

 tried to expel the transmission-idea, having thus the great 

 merit of breaking the ground for the setting in of more 

 unprejudiced inquiries. Galton, in his admirable little 

 paper of 1875, and Weismann, in his long series of fasci- 

 nating but dialectic publications, have suggested that the 

 elements responsible for inheritance (the elements of 

 Galton »s "stirp" or of Weismann 's "Keimplasma") 

 involve the different organs or tissue-groups of the indi- 

 vidual developing from the zygote in question. And 

 Weismann has furthermore built up an elaborate hypoth- 

 esis of heredity, suggesting that discrete particles of 



