thing, with tho pn.poi-tioii of tliow^ pci-ons of jrl\cn ajro who file in 

 tho course of a year, rrecisely this relative mortality rate de- 

 termines the slope of tho curve in the logarithmic figure, ior here, 

 as always, a given distance on the logarithmic scale denotes a cer- 

 tain proportion of change. Hence the more steeply the; logarithmic 

 curve descends, the higher is the relative mortality which it indi- 

 cates. PTencp, too, it is T)osMhle to pro^ide a key to the diagram in 

 the form of standard sample slope^s and corrcsi)onding numerical 

 death-rates, which liold true for all parts of the curve. 



From these tables and the diagrams, the followmg 

 points are to be noted: 



1. It is obvious that the laws of mortality are funda- 

 mentally similar in Drosophila to what they are in man, 

 with the one striking and outstanding difference that 

 since in the case of the Drosophila life tables we are deal- 



