260 Darwin, and after Darwin. 
the fixed laws of heredity, it further follows that the 
individuals composing each successive generation have 
a general tendency to be better suited to their sur- 
roundings than were their forefathers. And_ this 
follows, not merely because in every generation it is 
only the “ flower of the flock” that is allowed to breed, 
but also because, if in any generation some new and 
beneficial qualities happen to arise as slight variations 
from the ancestral type they will (other things per- 
mitting) be seized upon by natural selection, and, being 
transmitted by heredity to subsequent generations, will 
be added to the previously existing type. Thus the 
best idea of the whole process will be gained by com- 
paring it with the closely analogous process whereby 
gardeners, fanciers, and cattle-breeders create their 
wonderful productions; for just as these men, by 
always “selecting” their best individuals to breed 
from, slowly but continuously improve their stock, so 
Nature, by a similar process of * selection,” slowly but 
continuously makes the various species of plants and 
animals better and better suited to the conditions of 
their life. 
Now, if this process of continuously adapting or- 
ganisms to their environment takes place in nature 
at all, there is no reason why we should set any limits 
on the extent to which it is able to go, up to the 
point at which a complete and perfect adaptation is 
achieved. Therefore we might suppose that all species 
would eventually reach this condition of perfect 
harmony with their environment, and then remain 
fixed. And so, according to the theory, they would, 
if, the environment were itself unchanging. But for- 
asmuch as the environment (i.e. the sum total of the 
