276 THE AMERICAN NATURALIST [Vol. LVI 



the flies was stoppered tightly with the cork and left for 

 two minutes. Then the flies were turned out on a tile 

 and sexed and counted (since that operation corresponds 

 in extent of handling to what we need to do in making 

 up ma tings, etc.), then emptied into a vial with fresh 

 food, where they recovered from the ether in about half 

 an hour. For each successive group of flies a fresh bottle 

 and fresh cotton for the ether were of course used. 



In all other, here unspecified, particulars the technique 

 used in these ether experiments was uniformly that de- 

 scribed in detail in the first paper of this series (27). 



Seven series of experiments were conducted, differing 

 in respect of the number of times the flies were etherized, 

 and in their age at the time of etherization. The seven 

 series were as follows : 



A. Etherized once when one hour of age. 



B. Etherized once when twelve hours of age. 



B. Etherized once when three and a half days of age. 



E. Etherized twice when seven, and fourteen days of age, respectively. 



F. Etherized three times when seven, fourteen, and twenty-one days of 



age, respectively. 



G. Etherized four times when seven, fourteen, twenty-one and twenty- 



eight days of age, respectively. 



Data 



The Ix lines for the several series of etherized flies and 

 the controls are given in Table I. These L distributions 

 are calculated on the basis of 1,000 flies at emergence 

 from the pupal stage, with the absolute number of flies 

 on which the distribution is based given at the bottom 

 of the column in each ease. 



The Ix distributions for all etherized flies and for their 

 controls in the ether experiment, and for two tests of 

 the flies in line 101 and its continuation 107, are shown 

 graphically in Fig. 2. The data for the survivorship 

 lines in the two tests of line 107 are to be found in Pearl 

 and Parker (27). 



