CHAPTER II 

 EARLIER THEORIES OF HEREDITY 



It is probable that men have thought of heredity from 

 the earliest times, but so far as is known there was 

 no formulation of any definite theory of heredity before 

 the time of ARISTOTLE. Since that time there are 

 records of numerous theories of inheritance that may 

 well be regarded as wild speculations. They were 

 evolved with little or no basis of fact and of course are 

 not to be regarded as scientific. Some of these early 

 theories are interesting but not profitable for our pur- 

 pose. They developed from superstition rather than 

 from observation. 



It is evident also that inheritance in man first 

 attracted attention; later, animals were taken into 

 consideration. The study of inheritance in plants is of 

 comparatively recent development, due chiefly to the 

 fact that sex was not observed in plants until late in the 

 seventeenth century, and heredity was thought of only 

 in connection with sex. Even after sex in plants was 

 announced by CAMERARIUS in 1694 there was no general 

 belief in the claim until much later. For this reason 

 plant inheritance became a subject of observation and 

 theory, and the history of plant genetics began long 

 after the discovery of sex in plants. 



The earliest distinct theory of heredity which falls 

 within the period of modern biology was formulated 

 by DARWIN (i). This was published in 1868 in his 



