io An Examination of Weismannism. 



a different case from that of all the other constituent 

 parts of multicellular organisms, which contain within 

 themselves the doom of death. Furthermore, it appears 

 extremely probable that this doom of death has been 

 brought about by natural selection for the reasons 

 assigned by Weismann — namely, because it is for the 

 benefit of all species which perpetuate themselves by 

 sexual methods, that their constituent individuals 

 should not live longer than is necessary for the sake 

 of orginating the next generation, and fairly starting 

 it in its own struggle for existence. For Weismann 

 has shown, by a somewhat laborious though still 

 largely imperfect research, that there is throughout 

 all the metazoa a general correlation between the 

 natural lifetime of individuals composing any given 

 species and the age at which they reach maturity, 

 or first become capable of procreation. This general 

 correlation, however, is somewhat modified by the 

 time during which progeny are dependent upon their 

 parents for support and protection. Nevertheless, 

 it is evident that this fact tends rather to confirm 

 the view that expectation of life on the part of 

 individuals has in all cases been determined with 

 strict reference to the requirements of propagation, 

 if under propagation we include the rearing as well 

 as the production of offspring. I may observe in 

 passing that I do not think this general law can 

 be found to apply to plants in nearly so close 

 a manner as Weismann has shown it to apply to 

 animals ; but, leaving this consideration aside, I think 

 that Weismann has made out a good case in favour 

 of such a general law with regard to animals \ 



1 See Appendix. 



