CHAPTER I 

 THE BACKGROUND OF GENETICS 



Genetics, or the experimental study of heredity, was 

 an outgrowth of the study of evolution. A ver>' ])ricf 

 survey of the subject of evolution before 1900 will serve, 

 therefore, to provide a background for the material of 

 the present text, by depicting something of what was 

 going on in the minds of biologists at the time that 

 genetics had its birth. It will also be useful to have before 

 us some of the ideas of evolution as a means of suggesting 

 a wider application of the principles of genetics that are 

 to be taken up. 



Nothing need be said here of that phase of the evolu- 

 tion enterprise which concerned itself with convincing 

 a doubting public of the mere fact of evolution. The 

 other phase, involving the presentation of ex})lanations 

 of the evolutionary process, will be sketched briefly. 



The vague ideas of evolution that occupied the minds 

 of men during the earKer history of biology and the fan- 

 tastic speculative explanations that were proposed have 

 Httle more than historical interest for us today. These 

 explanations were based upon meditation rather than 

 investigation, so that they resembled philosophy rather 

 than science. 



Around the latter part of the eighteenth ccntur\', 

 certain men (notably Erasmus Darwin, Goetiik, and 

 St. Hilaire) developed more accurate notions of evolu- 

 tion, based in good part upon their own observations, 



I 



nOFBRTY LIBRARY 



n. C. State CoUem 



