106 ANIMAL INDIVIDUALITY [CH. 



first seen in compound individuals between the re- 

 productive functions on the one side and all the rest 

 on the other. In other words, one sort of cell is 

 concerned entirely with the species, the other entirely 

 with the separate individuals of which the species 

 consists ; to use the current phraseology, the one sort 

 is germinal, the other somatic. The word somatic 

 opens up another view : Volvox is the first organism 

 which, in the ordinary sense of the word, has a mortal 

 body. Its substance is not passed on unimpaired 

 from individual to individual, but with each act of 

 generation the major part must die, sacrificed for the 

 greater efficiency of the race. 



In Volvox, this body consists of but one sort of 

 cell : in all the organisms usually known as Metazoa 

 there are at least two sorts, if not more. Besides the 

 division of labour between germ and soma, there is 

 developed another in the soma itself, at the first 

 between protective and nutritive cells, the one form- 

 ing an outer covering round the other, which in its 

 turn surrounds an internal cavity. But even if Volvox 

 only possesses species-individuality, the individuality 

 is none the less real ; and the fact that in the family 

 Volvocidae we can positively affirm that the step from 

 an aggregate to a higher individual has actually taken 

 place, is one of the most important in biology. 



This, however, is not the only way in which the 

 second grade can or has been reached. It is quite 



