REGENERATION AND DEATH 215 



occur, so far as we at present know, as a natural and 

 necessary result of life. Death with them is purely 

 the result of an accident, some external cause. Our 

 existing science leads us therefore to the conception 

 that natural death has been acquired during the pro- 

 cess of evolution of living organisms. 1 Why should 

 it have been acquired ? You will, I think, readily 

 answer this question, if you hold that the views which 

 I have been bringing before you have been well de- 

 fended, by saying that it is due to differentiation, 2 

 that when the cells acquire the additional faculty of 

 passing beyond the simple stage to the more com- 

 plicated organisation, they lose some of their vital- 

 ity, some of their power of growth, some of their 

 possibilities of perpetuation ; and as the organisation 

 in the process of evolution becomes higher and 

 higher, the necessity for change becomes more and 

 more imperative. But it involves the end. Differen- 

 tiation leads up, as its inevitable conclusion, to death. 

 Death is the price we are obliged to pay for our 

 organisation, for the differentiation which exists in us. 

 Is it too high a price ? To that organisation we are 

 indebted for the great array of faculties with which 

 we are endowed. To it we are indebted for the 

 means of appreciating the sort of world, the kind of 

 universe, in which we are placed. To it we are in- 



1 On death among Protozoa see Appendix No. III. 



2 The theory that natural death is the incidental result of cellular differentia- 

 tion was first put forward by me in 1885 ; compare Proceedings American 

 Association Adv. Science, vol. xxxiv., p. 311. 



