2 PHYSIOLOGICAL GENETICS 



(•(instantly for interpretative hypotheses which are sometimes 

 difficull to prove. This constitutes simultaneously the danger 

 and the charm of the work in this line. The effect has been thai 

 comparatively few geneticists were attracted to this difficult 

 field and that those who were had to labor in the dark. Thus, 

 the part of genetics that to me is the most interesting was 

 practically banned from advanced treatises and textbooks of 

 genetics, and the opinion has developed and has even been voiced 

 that it is not worth while to mention a field in which nothing is 

 known with certainty. But the history of science teaches us 

 that it is just such borderline fields of today that will bear the 

 fruits of tomorrow. Fortunately the negative attitude has begun 

 to change considerably, and more and more workers of the younger 

 generation are attracted to the problems of physiological genetics. 

 It might therefore be useful to put together the known facts and 

 to link them into a picture, knowing that this picture will be 

 subject to many changes and improvements even in the near 

 future. 



