SHULL: GENETICS 129 



major fields of biology could bring supporting evidence, gave a still stronger 

 bond of unity among the several branches of biological science. Taxonomy, 

 comparative anatomy, embryology and paleontology w^ere the chief sources of 

 this supporting evidence. 



It remained to secure convincing evidence of the evolutionary processes 

 from actual experimentation, and here v^e can not over-stress the indebtedness 

 of the entire biological world to that great genius of simplicity, philosophical 

 outlook, penetrating vision and energetic persistent labor, Hugo de Vries, 

 whose work more than that of any other individual ushered in a new era in 

 biological science and philosophy. Thus was born the new experimental science 

 appropriately called for a time "experimental evolution," but felicitously 

 christened by William Bateson in 1906, the science of "Genetics." Inter-rela- 

 tionships of plant groups and of animal groups took on a new and more funda-' 

 mental meaning when analyzed by the simple means provided by the experi- 

 ments of Mendel and De Vries. There came in this way a clarification of con- 

 cepts, and the possibility of brushing aside fallacious doctrines and their re- 

 placement by experimentally tested facts. 



From another direction came independently another fundamental element 

 of genetical technology. Contemporaneous with the work of Mendel and of 

 De Vries was the statistical attack on problems of evolution, brilliantly con- 

 ceived and put into practice by Sir Francis Galton, a cousin of Charles Darwin. 

 This was the technique of the mathematical analysis of populations later de- 

 nominated "Biometry." 



Although Galton's conclusions seemed at first to be at variance with the 

 discoveries of Mendel, the work of the genial and brilliant Danish plant phys- 

 iologist, W. Johannsen, on pure-lines and populations in beans disclosed the 

 nature of the discrepancy and brought complete harmony between the ob- 

 servations of Galton and those of Mendel and thus helped to establish biometry 

 as one of the fundamental biological techniques. The tool thus developed for 

 the handling of population problems may be considered not the least of the 

 contributions which genetics has made to the other sciences, most of which 

 tend to become more and more statistical as their stores of basic materials 

 grow in magnitude and diversity. 



One of the most important discoveries which resulted from the experi- 

 ments of De Vries was the demonstration that variations, which Darwin had 

 taken for granted and had assumed to be more or less generally transmitted 

 from parents to offspring, are of two kinds. Some are completely inherited 

 and remain permanent elements of organization in subsequent generations 

 while others are non-inheritable and promptly disappear from subsequent 

 generations. This important differentiation of variations into inherited and 

 non-inherited, respectively designated "mutations" and "fluctuations," was 

 beautifully and convincingly confirmed by Johannsen, whose keen analytical 



