THE CELLULAR BASIS 97 



they are the result of reasoning about names 

 rather than facts, of getting far from phen- 

 omena and philosophizing about them. The 

 comparison of heredity to the transmission of 

 property from parents to children has pro- 

 duced confusion in the scientific as well as in 

 the popular mind. It is only necessary to re- 

 call the most elementary facts about develop- 

 ment to recognize that in a literal sense 

 developed characteristics of parents are never 

 transmitted to children. 



2. The Transmission Hypothesis. — And 

 yet the idea that the characteristics of adult 

 persons are transmitted from one generation 

 to the next is a very ancient one and was uni- 

 versally held until the most recent times. Be- 

 fore the details of development were known 

 it was natural to suppose, as Hippocrates did, 

 that white-flowered plants gave rise to white- 

 flowered seeds and that blue-eyed parents pro- 

 duced blue-eyed germs, without attempting to 

 define what was meant by white-flowered seeds 

 or blue-eyed germs. And even after the facts 

 of development were fairly well known it was 

 generally held that the germ cells were made 



