142 LIFE AND DEATH. 



after the extrusion of the reproductive cells, were unable to feed 

 any longer or at any rate to an adequate extent ; and that the cause 

 of their death did not lie in their constitution, but in the unfavour- 

 able conditions which surrounded them. This is not so much a 

 process of natural death as of artificial death, regularly appearing 

 in each individual at a corresponding period, because, at a certain 

 time of life, the ocganism becomes influenced by the same un- 

 favourable conditions. It is just as if the conditions of life in- 

 variably led to death by starvation at a certain stage in the life 

 of a certain species. But we know that death arises from purely 

 internal causes among the higher Metazoa, and that it is antici- 

 pated by the whole organisation as the normal end of life. Hence 

 nothing is gained by this explanation founded on the Ortho- 

 nectides, and we should have to seek further and in a later stage 

 of the development of the Metazoa, for the internal causes of true 

 natural death. 



Another theory might be based upon the supposition that natural 

 death has been derived, in the course of time, from an artificial 

 death which always appeared at the same stage of each individual 

 life as we have supposed to be the case in the Orthonectides. I 

 cannot agree with this view, because it involves the transmission of 

 acquired characters, which is at present unproved and must not be 

 assumed to occur until it has been either directly or indirectly de- 

 monstrated 1 . I cannot imagine any way in which the somatic 

 cells could communicate this assumed death by starvation to the 

 reproductive cells in such a manner that the somatic cells of the 

 resulting offspring would spontaneously die of hunger in the same 

 manner and at a corresponding time as those of the parent. It 

 would be as impossible to imagine a theoretical conception of such 

 transmission as of the supposed instance of kittens being born 

 without a tail after the parent's tail had been docked ; although 

 to make the cases parallel the kittens' tails ought to be lost at the 

 same period of life as that at which the parent lost hers. And 

 in my opinion we do not add to the intelligibility of such an 

 idea by assuming the artificial removal of tails through hundreds 

 of generations. Such changes, and indeed all changes, are, as I 

 think, only conceivable and indeed possible when they arise from 

 within, that is, when they arise from changes in the reproductive 

 1 See the preceding essay ' On Heredity.' 



