OUTSTANDING BIOLOGICAL ADVANCES 35 



which hereditary qualities are passed from genera- 

 tion to generation and the conditions under which 

 they are transmitted and by which they are qualified. 

 This has led to much speculation and the formulation 

 of various temporary theories of heredity that have 

 given way to better ones. It is a long and involved 

 story to trace the transformations of these theories, 

 but, it may be said in a word, that, in the last decade 

 of the nineteenth century, they were replaced by the 

 theory of germinal continuity one of the most 

 fruitful ideas of nineteenth century zoology. This 

 idea will be returned to under the evolution theory of 

 Weismann. 



The theories referred to were chiefly the result of 

 speculative thinking, and more promising avenue?* 

 were opened through the application of experiment. 



The application of experimental and of statistical 

 methods to the study of heredity was brought about 

 chiefly by two men Francis Galton, the English* 

 man, and Gregor Mendel, an Austrian monk. 



Although Mendel conducted his experimental ob- 

 servations of heredity and published his results 

 (1866-1867) before Galton had fairly begun, we 

 shall see that Galton's results got into notice before 

 those of Mendel and began to influence progress. 



