418 



THE AMERICAN NATURALIST [Vol. XLIX 



While it is true in the first count above that when ab- 

 normality entered through the egg there was greater ab- 

 normality in the offspring, yet this is offset by the counter 

 evidence in this set that the change to the usual pheno- 

 type took place sooner in this set than in the others. 

 This point will be taken up again in connection with other 

 data. 



In order to compare, under changing conditions, hetero- 

 zygous and homozygous females, some white abnormal 

 females were mated to red abnormal males, and, inde- 

 pendently, some other white abnormal females were 

 mated to red normal males. After several days both 

 kinds of females were separated from their respective 

 males and put together into a single new bottle. All of 

 the daughters had red eyes. In the first count two types 

 of females could readily be distinguished. Some were 

 quite abnormal, others were slightly abnormal or normal. 

 In the second count (next day) again two types appeared, 

 one quite abnormal and the other slightly abnormal fe- 

 males. In the third count some females were fairly ab- 

 normal, the rest normal and this held for the fourth 

 count. The result leaves little doubt that under these con- 

 ditions, the homozygous were abnormal and the hetero- 

 zygous less abnormal or quite normal. 



In order to see if the factors for red and for white 

 affect the condition of the zygote, homozygous for ab- 

 normal; white abnormal females were mated to red ab- 

 normal males, and, separately, other white abnormal fe- 

 males to white abnormal males. After several days the 

 females were put together in a new bottle and the males 

 removed. Through five consecutive counts the red and 

 the white daughters were alike, at first quite abnormal, 

 later nearly normal. Eed and white abnormal females 

 therefore behave alike. 



PRESENCE AND ABSENCE 



It is not without interest to examine the bearing of 

 these results from the point of view of the "presence 



