392. 



THE QUARTERLY REVIEW OF BIOLOGY 



general biological principles which we 

 shall find operating in these lower forms 

 relative to longevity also apply, in some 

 degree, to the determination of the human 

 life span, but I am not prepared positively 

 to assert that this is so in this particular 

 case. There seems to me to be some 



humanity, it is subject to the same laws 

 as those which govern the animals from 

 which it has arisen." 



LIFE TABLES 



The simplest experiment that can be 

 performed about longevity is to take a 



\^ l,ns/07 99 



Fig. i. Showing the Number of Fruit Flies Surviving at Different Ages, out of iooo Starting Imaginal 



Life Together 

 The upper pair of lines relate to the normal wild type Drosophila, and the lower pair to the mutant vestigial 



probability that it is so, but how great 

 this probability is cannot be precisely 

 evaluated in the present state of knowl- 

 edge. I have confidence, however, in the 

 general biological principle recently stated 

 by J. B. S. Haldane in these words: 

 ' 'Whatever additional facts may be true of 



considerable number of individual organ- 

 isms, say a thousand fruit flies (Dro- 

 so-phila), at the moment of birth (which 

 we shall for convenience in the case of 

 Drosophila take as the moment of emer- 

 gence as imago from the pupa case), 

 confine them in suitable receptacles for 



