274 DEATH 



by boiling the water in which it is contained ; but 

 it does not, in the ordinary course of events, die. 

 The production of one generation involves the dis- 

 appearance but not the death of the parent genera- 

 tion. From the first Amceba to the present day 

 there has been direct continuity of living matter. 

 Death may occur through violence, but it is not a 

 necessary accompaniment or consequence of life. 

 Moreover death, when it does happen in the case 

 of an Amceba, causes a final interruption, an abso- 

 lute break in the chain. No Amceba that has died 

 has left offspring, for such offspring can only arise 

 by the division of the living body of the parent. 

 " No Amceba," it has been well expressed, " has 

 ever lost an ancestor by death." 



The above considerations, which clearly apply 

 not only to Protozoa but to any other animals which 

 reproduce by fission, form the basis on which Weis- 

 mann has built up his theory of the origin of death. 

 This theory may be briefly summarised as follows : 

 Protozoa, reproducing by fission, are immortal in 

 the sense that death does not occur as a necessary 

 or natural termination of the life-cycle. Natural 

 death must therefore be limited to Metazoa, or 

 multicellular animals. In Metazoa a distinction is 

 always found between somatic cells and reproduc- 

 tive cells ; the former being the component elements 

 of which the body of the individual is constructed, 

 while the latter are the units from which the 

 individuals of the next succeeding generation will 

 be developed. The somatic cells are concerned 

 with the existence and welfare of the individual ; 



