III.] LIFE AND DEATH. 1 37 



forms.' I have not however as yet attempted to think out in 

 detail such processes of natural selection as would limit the 

 somatic part of the Metazoan body to a short term of existence, 

 and I only wished to emphasize the general principle lying at 

 the basis of the whole process, without stating the precise 

 manner in which it operates. 



If I now attempt to take this course, and to reconstruct 

 theoretically the gradual appearance of natural death in the 

 Metazoa, I must begin by again alluding to Gotte's criticisms in 

 reference to the operation of natural selection. 



I consider death as an adaptation, and believe that it has 

 arisen by the operation of natural selection. Gotte\ however, 

 concludes from this that 'the first origin of hereditary and 

 consequently (for the organization in question) necessary death, 

 is not explained but already assumed.' 'The operation and 

 significance of the principle of utility consists in selecting the 

 fittest from among the structures and processes which are at 

 hand, and not in directly creating new ones. Every new 

 structure arises at first, quite independently of any utility, from 

 certain material causes present in a number of individuals, and 

 when it has proved useful and is transmitted, it extends, 

 according to the laws of the survival of the fittest, in the group 

 of animals in which it appeared. This extension will undergo 

 further increase with every advance in utility which results 

 from further structural changes, until it extends over the whole 

 group. So that usefulness effects the preservation and the 

 distribution of new structures, but has nothing whatever to do 

 with the causes of their primary origin and their consequent 

 transmission to all other individuals. Indeed, on these heredi- 

 tary causes the necessity of the structures in question depends, 

 so that their usefulness in no way explains their necessity.' 



'These conclusions, when applied to the origin of natural 

 death called forth by internal causes, would show that it became 

 inevitable and hereditary in a number of the originally immortal 

 Metazoa, before there could be any question as to the benefits 

 derived from its influence. Such influence must have consisted 

 in the fact that more descendants survived the struggle for 

 existence and were able to enter upon reproduction among the 

 individuals which had inherited the predisposition to die than 



^ 1. c, p. 5. 



