136 ANIMAL INDIVIDUALITY [CH. 



compensated for by the formation of a totally new 

 individuality, rudimentary though it be. If the parts 

 of the system, instead of being related by but one 

 tie and for a short space only, were to be brought 

 into relation for the whole of their lives, the resulting 

 system would have the chance of becoming not only 

 more harmonious, but even a more independent 

 individuality than was either of its parts before their 

 mutual adaptation a consummation actually realized 

 in the Lichens. 



This necessity for the parts of a compound in- 

 dividual to lose their own independence for the 

 ultimate greater independence of the whole this 

 increasing mutual parasitism of the units within an 

 individual is in fact a brief statement of the main 

 facts observable concerning internal differentiation. 

 Internal differentiation, indeed, to be strictly accurate, 

 is the only way in which individuals are formed, for 

 aggregate differentiation is only a convenient label 

 for the combination of two processes first the forming 

 of an aggregate, be it of molecules, cells, or persons, 

 and then the welding of this mere aggregate into a 

 true individual by means of internal differentiation. 



The progress of the individual of the second grade 

 is in essence a progress towards greater complexity, 

 more harmonious co-ordination, higher independence ; 

 this is revealed to the eye in the multiplication and 

 specialization of its various kinds of cells. When it 



