150 HEREDITY AND SELECTION IN SOCIOLOGY 



of the daughter cells reproduces all the qualities of the parent 

 organism, and each in turn goes through the process of division. 

 Unicellular organisms multiply in regular progression — 1, 2, i, 

 8, 16, 32, and so forth — but each organism is in itself immortal ; 

 that is to say, it does not succumb to the wear and tear of Ufe, 

 but simply divides into two when it reaches a certain limit of 

 growth. There is no death of the organism in the physiological 

 sense of the word — except that form of death which is due to 

 external and accidental causes ; in fact, for the Protozoa death 

 is not a constitutional necessity, and every Protist is potentially 

 immortal. Death is a physiological phenomenon which is not 

 by any means intrinsically bound up with organic life as such, 

 but is introduced at a later stage of evolution, as a consequence 

 of that evolution. It is a result of the division of labour.^ 



For it must be remembered that, in the case of the Metazoa, 

 it is the soma alone which is subject to the physiological necessity 

 of death ; the germ-plasm is immortal. The somatic cells of the 

 organism are mortal ; they die, and must necessarily die, for 

 their preservation would be of no use whatever to the species in 

 the struggle for existence. In the case of these compUcated 

 organisms it would be impossible for reproduction to be effected 

 by fission ; and it would be equally impossible to effect the 

 integral transmission of the parent organism to each of the 

 progeny. The growth and compUcation of the organism, the 

 ever-increasing division of labour among the parts, require that 

 a distinct substance be set apart for the reproduction of the 

 species. We have seen that this substance is the chromatin 

 substance in the nucleus of the germ-cells ; and this germ sub- 

 stance is immortal. It transmits itself integrally from one 

 generation to another, and this transmission is essential for the 

 continuity of the species. 



Thus we see that death is a direct consequence of differen- 



1 Weismann, VoHrdge iiber Deszendenztheorie, i. 211-214; A. Dastre, 

 La Vie et la Mort, pp. 325 ff. Paris, 1905. 



