EXPERIMENTAL STUDIES ON THE DURA- 

 TION OF LIFE 



II. Hekeditary Diffeeences in Dueation of Life tn 

 Line-bred Strains of Drosophika.^ 



PEOFESSOE EAYMOND PEARL AND SYLVIA L. PAEKER 



Introduction 



It was shown in the first paper in this series (27)^ that 

 there was a marked difference in mean duration of life, 

 and in the form of the L curve, between wild-type stocks 

 of DrosopJiila on the one hand and the synthetic quin- 

 tuple mutation stock on the other hand. It was further 

 made clear that, because of the technique used in the ex- 

 perimental work, there could be no doubt that the basis of 

 this difference must be hereditary and not environmental. 

 Furthermore, Hyde (11) and Pearl (6) have presented 

 evidence for the Mendelian inheritance of this character 

 duration of life. 



Given it to be the fact, as the just cited work demon- 

 strates to be the case, that there are hereditary differ- 

 ences within the same species of Drosophila in respect of 

 duration of life, the problem which next presents itself is 

 to determine whether tvithin a particular strain of Droso- 

 pJiUa hereditary differences exist, and if so what their 

 magnitude may be, their deg'ree of ])( rmaiieiico, etc. In 



