192 



BIOLOGY OF DEATH 



using this term "bom" to denote emergence from the 

 pupal stage as imagines. Each following day these small 

 bottles are inspected. Whenever a dead fly is found, it 

 is removed and a record made in proper form of the 

 fact that its death occurred, and its age and sex are noted. 

 Finally, when all the flies in a given small bottle have 

 died, that bottle is discarded, as the record of the duration 



■36 4Z 4d £4 60 66 72 7B 84 30 



ABC IN IMVS 



Fia. 48. — ^Life lines for different inbred lines of descent in DrosophUa. 



of life of each individual is then complete. All the < 

 bottles are kept in electric incubators at a constant 

 temperature of 25° C, the small bottles being packed for 

 convenience in wire baskets. All have the same food 

 material, both in quality Eind quantity, so that the envi- 

 ronmental conditions surrounding these flies during their 

 life may be regarded as substantially constant and uni- 

 form for all. 



Figure 48 shows the survival frequency, or Ix line 

 of a life table, for six different lines of Drosophila, which 

 have been bred in my laboratory. Each line represents 



