PROTOZOA 307 



does not build up a temporary body-shell, but only germ- 

 cells. These are, of course, bodies, but there is nothing 

 temporary formed from them ; they in turn create only 

 cells that have the power to live on. Every protozoon 

 multiplies by dividing into two. If dangers are avoided, 

 these animals will continue to live, divide into others, 

 and so on ; in a word, it is possible that one of these 

 animals may never become a corpse. The protozoa 

 seem to have, as Weismann puts it, a potential 

 immortality ; that is to say, they have in their frame 

 a capacity for living indefinitely. This is, of course, 

 only a capacity. No one questions that they may come 

 to a violent end. But it is not in the nature of their 

 structure that they are menaced with senile decay and 

 death, and that life itself gradually uses up their sub- 

 stance, as is the case with the body-cells of the higher 

 animals. 



It has been objected to this view, that the protozoa 

 have no natural death, that at each cleavage the indi- 

 viduality of the mother comes to an end. " Individual " 

 means "indivisible," and it is clear that the mother dies 

 when it divides into two daughters, as these are two new 

 individuals. 



Weismann, however, considers that the characteristic 

 of death is not the destruction of individuality, but the 

 appearance of a corpse. We will not stay to discuss 

 whether this conception is correct, but will go to the 

 heart of the problem. The protozoa have, Weismann 

 says, the faculty of not being permanently used up by 

 metabolism, and this can be called metaphorically, with 

 some propriety, immortality. But is there really in the 



