388 



THE AMEBIC AX NATURALIST 



[Vol. XLIX 



The preceding case shows that there is no necessary 

 relation between the development of the abnormality in 

 the parent and that in the offspring. This is only a 

 sample of a large amount of similar data. But this evi- 

 dence does not show what special conditions make for ab- 

 normality. In order to study this problem I generally 

 used heterozygous females which were obtained either 

 by mating an abnormal male to a wild (virgin) female 

 (in which case the daughters will be abnormal under suit- 

 able conditions and the sons normal), or reciprocally by 

 mating a normal male to an abnormal female (when all 

 the daughters will be abnormal (heterozygous) and all 

 the sons pure abnormal). Many experiments had shown 

 that the heterozygous female changes over more promptly 

 to the normal character than does the homozygous male 

 and the latter sooner than the homozygous female. 



The one outstanding fact for some time was that as a 

 bottle crowded with flies gets old there is always a change 

 from day to day from abnormal towards normal, but it 

 remained to be shown whether the change was due to 

 the drying out of the culture, or to any one of a dozen 

 other parallel changes that obviously are going on at the 

 same time. The more significant results of a prolonged 

 set of experiments may be summed up as follows : 



1. Starvation. — Lack of food does not bring about the 

 change from abnormal to normal. Flies that are so 

 starved as to be extremely small may be very abnormal. 



2. Acid, Alkali or Neutral Condition of Food Stuff. — 

 Most cultures change in the course of the ten to twelve 

 days from an acid through a neutral to an alkaline con- 

 dition. Fresh fermenting banana (in the old and acid 



