308 DARWINISM AND THE PROBLEMS OF LIFE 



protozoa nothing that ever compels them to become 

 corpses ? This seems to be correct. There can be no 

 such necessity in the protozoa, otherwise there would be 

 no protozoa to-day that are fragments of their ancestors, 

 though the parts have fully developed in turn. When 

 a protozoon is split into two daughters there is certainly 

 no corpse to be seen, and it is the same when the 

 daughters in turn subdivide. Here we have a difference 

 between unicellulars and multicellulars. In the latter 

 it is only the small particles in the germ-cells that are 

 immortal. The germs divide. But only one part, the 

 newly divided germ-cells, have the power to carry on 

 the life. The other part, the body-cells, are used up 

 by metabolism, and must perish. The unicellulars 

 divide, but in their case both halves can carry on the 

 life indefinitely. 



Natural death is not, therefore, a necessity for all 

 organisms, but has only made its appearance with the 

 multicellulars. In their case the germ-cells convey the 

 living substance to their descendants ; when they leave 

 the body, it is useless for the maintenance of the species, 

 as it has not the power to create new organisms. 

 Weismann believes that we have here the chief 

 reason of the introduction of death into the organic 

 world. The body becomes superfluous and disappears, 

 like all useless organisms, when it has secured the 

 maintenance of the species by the transmission of its 

 germ-cells. However that may be, we see that the 

 division of labour amongst the several groups of body- 

 cells could not be very considerable unless they made 

 no claim to indefinite duration. Many cells, in fact, have 



