EPOCHS IN BIOLOGICAL HISTORY 405 



biology, and the now famous Mendelian laws of inheritance 

 were unknown to science until 1900, when other biologists, 

 coming to similar results, unearthed his forty-year-old paper. 

 We have already seen that the fundamental principle of the 

 segregation of the genes of 'alternative' characters in the 

 germ cells, which Mendel's work indicated, has been ex- 



FIG. 208. Gregor Johann Mendel. 



tended to other plants and to animals, and that instead of 

 being, as at first thought, a principle of rather limited ap- 

 plication, has come to be the key to all inheritance. And 

 the present results are extremely convincing because cyto- 

 logical studies on the architecture of the chromosome com- 

 plex of the germ cells keep pace with and afford a picture 

 of the physical basis of inheritance the mechanism by 

 which the segregation and distribution of characters by the 



