THE LAW OF JOHANNSEN. 205 



tative instability of the genes, must be explained by the wish 

 to try out to the full a biomechanic theory of inheritance and 

 life rather than to fall back upon a vitalistic one, which must 

 be as sterile as on the face of it may seems satisfactory. 



The hypothesis, that the genes are relatively simple sub- 

 stances with autokatalytic properties, has the advantage over 

 a vitalistic conception of genes, that it is a hypothesis which 

 can be worked with, even though it may not be found to work 

 in all cases. 



The question as to the fundamental qualitative stability of 

 the genes themselves is to my mind of the very first import- 

 ance, and all our work of the last years has been planned so as 

 to shed light on this point. It is indeed remarkable to observe 

 the casual way in which Geneticists who themselves perform 

 experiments, the results of which have a very direct relation to 

 the subject, refer to the problem. Vitalism has a very strong 

 grip upon the minds of most of the Geneticians. 



If we observe great differences between cells and cell-com- 

 plexes in their reaction upon the direct environment, and we 

 have to admit that nevertheless the personnel of the genes is 

 identical in these cells, must we conclude that such differences 

 are due to the inclusion in some substances or physical re- 

 lationships as foreign to the protoplasm of the other cells as a vi- 

 tal dye, or as the effects of a pressure between two platesof glass ? 



If we use the hypothesis, that the genes are not in themselves 

 living, but chemical things, we can conceive of protoplasm as a 

 combination of substances which each have the property of 

 being a katalyzer for its own synthesis, and which can there- 

 fore reproduce themselves quantitatively without changing 

 qualitatively. And we can imagine how this combination, pro- 

 toplasm, derives its physical properties from inter-relations 

 between several of its constituents. In other words, it is wholly 

 unnecessary to conceive of protoplasm as of something dis- 

 tinct from, and including genes, but it is both simpler and bet- 

 ter in accord with all the facts to conceive of protoplasm as of 

 the sum total of the genes. 



