The Mechanistic Conception of Life 23 



The main task which is left here for science to accomplish is 

 the determination of the chemical substances in the chromo- 

 somes which are responsible for the hereditary transmission of 

 a quality, and the determination of the mechanism by which 

 these substances give rise to the hereditary character. Here 

 the ground has already been broken. It is knowTi that for the 

 formation of a certain black pigment the cooperation of a 

 substance — tyrosin — and of a ferment of oxidation — tyrosinase 

 — is required. The hereditary transmission of the black color 

 through the male animal must occur by substances carried in 

 the chromosome which determine the formation of tyrosin or 

 tyrosinase or of both. We may, therefore, say that the solu- 

 tion of the riddle of heredity has succeeded to the extent that 

 all further development will take place purely in cytological 

 and physico-chemical terms. 



While until twelve years ago the field of heredity was the 

 stamping ground for the rhetorician and metaphysician it is 

 today perhaps the most exact and rationalistic part of biologj', 

 where facts cannot only be predicted qualitatively, but also 

 quantitatively. 



VII. THE harmonious CHARACTER OF THE ORGANISMS 



It is not possible to prove in a short address that all life 

 phenomena will yield to a physico-chemical analysis. We have 

 selected only the phenomena of fertilization and heredity, since 

 these phenomena are specific for living organisms and without 

 analogues in inanimate nature; and if we can convince our- 

 selves that these processes can be explained physico-chemically 

 we may safely expect the same of such processes for which 

 there exist a-priori analogies in inanimate nature, as, e.g., for 

 absorption and secretion. 



We must, however, settle a question which offers itself 

 not only to the layman but also to every biologist, namely, how 

 we shall conceive that wonderful ''adaptation of each part to the 



