158 THE STORY OF LIFE'S MECHANISM. 



have produced different combinations and associa- 

 tions, so that Pekin is wonderfully unlike London. 

 So in these early developing machines, quite a 

 variety of method of organization was adopted 

 by the different groups. Now as soon as any 

 special type of organization was adopted by any 

 animal or plant, the principle of heredity trans- 

 mitted the same kind of organization to its de- 

 scendants, and there thus arose lines of descent 

 differing from each other, each line having its 

 own method of organization. As we follow the 

 history of each line the same thing is repeated. 

 We find that the representatives of each line 

 again separate into groups, each of which has 

 acquired some new type of organization, and 

 there has thus been a constant divergence of 

 these lines of descent in an indefinite number 

 of directions. The members of the different 

 lines of descent all show a fundamental likeness 

 with each other since they retain the fundamental 

 characters of their common ancestor, but they 

 show also the differences which they have them- 

 selves acquired. And thus the process is re- 

 peated over and over again. This history of the 

 growth of these different machines has thus 

 been one of divergence from common centres, and 

 is to be diagrammatically expressed after the 

 fashion of a branching tree. The end of each 

 branch represents the highest state of perfection 

 to which each line has been carried. 



One other point in this history must be noted. 

 As the development of the complication of the 

 machine progressed the possibility of further 

 progress has been constantly narrowed. When 



