THE KINSHIP OF LIFE. 31 
plants can live has been thousands of times discovered, 
its colonization a thousand times attempted. In these 
efforts there is no co-operation. Every individual is for 
himself, every struggle a struggle for life and death. 
To each species each member of every other species is 
an alien and a savage. 
The study of geographical distribution shows the re- 
lations of creative processes to space. The forms in- 
habiting one district arethe children of 
the earlier inhabitants. The survival 
of these forms is due to that which I 
have elsewhere called the “ survival of the existing,” for 
it is certain that in any part of the world a totally dif- 
ferent grouping of animals or plants would have been 
equally fitted to the environment. The laws of geo- 
graphical distribution may be summed up thus: The 
reason why any given species of animal or plant is 
not found in a given district is (2) because it could not 
get there from its own habitat, or (4), being there, it 
could not maintain itself either in competition with 
others or from the stress of environment, or else (c) it 
‘has in maintaining itself- become altered into a distinct 
species. 
In like manner the facts of geological distribution 
have a meaning when we view them in the light of the 
theory of descent. The birth, increase, 
decline, and final change or disappear- 
ance of species or types in geological 
history are necessary parts of the Darwinian theory. 
They would be inexplicable on any other hypothesis. 
These changes represent the survival of the fittest as 
related to time. With the lapse of time come changes 
in environment, and these changes produce correspond- 
ing changes in animal or plant life. But these changes 
on the earth and in its life are for the most part gradual 
4 
Survival of 
the existing. 
Geological dis- 
tribution. 
