508 



THE AMERICAN NATURALIST [Vol. LV 



Summary 



This paper is tlie first in a series of experimental 

 studios on tlic factors influencing the duration of life in 

 Droso/Jiihi iin linindiistcr. An account of the experimen- 

 tal tcrlii;i,,ii.- i,^<-(| ill these duration of life studies is 

 pivx.nt.Ml. l''oni- r.)tnpl<*te life tal)l.'s l'..r Dmsophiln nn^ 

 o-iveii, and it is shown tiiat this or-aiiiMi. tolh.xv- (|ua!i- 

 titativcly the >aiu(' ,uvi,..i-;, 1 la\\ It, i.-p.M-i ..f il,.. di^- 

 trihutioii of its nioHalitx a^ do... in.ni. thi^ work 



deals only with the (hiraiiot, nf Ilf,. In 



there is no compoiiciil in the lii'c i.'ihlcs coni'spond- 

 ing to the mortality of infain-x and chihlhood in man. l! 

 is shown that there are wi(h' ditfercnccs in (hiration of 

 life in different stocks of Drosophila, and that the l)a>is 

 of these differences is hereditary and not en\ ironinent;d. 

 The Drosophila survival line ot the life tal)le (/,) runs in 

 general throughout its course between human survi\al 

 lines of (a) the present time, and ih) about the beginning 

 of the Christian era (Macdonell's data fi-om Konian 

 Africa), the curves being supei-})os(Ml (ni the l)asis of the 

 omission of the human mortalil.v ol' int'aiic> and chihl- 



