210 FOOT-NOTES TO EVOLUTION. 
months’ sleep. These little trees are the Lapps of forest 
vegetation. 
All natural history is full of similar cases of modifi- 
cations, Everywhere there is the most perfect adapta- 
tion of life to its conditions, But this adaptation must 
come about through the survival of those organisms 
fittest to live under the conditions, while the unfit die 
out and leave no progeny. But fitness is a relative 
term; for in many cases, as with the Norwegian dwarf 
birches, the deformed or stunted may be the only ones 
fitted to survive. An advantage ever so slight must in 
: the long run conquer. 
The arctic birches serve as one illustration only of 
the spread and change of organisms in the face of bar- 
riers apparently insurmountable. I can 
not enter into details as to the many 
ways in which individuals manage to 
cross the barriers which usually limit the species. These 
ways are as varied as the creatures themselves, and in- 
finitely more varied than the barriers. By the long- 
continued process of adjustment to circumstances, with 
the incessant destruction of the unadapted, the various 
organisms have become so well fitted to their surround- 
ings as to give rise to the popular impression that each 
species now inhabits that part of the world best fitted 
for its occupation, Yet the very reverse of this must 
be true, for in the growth of any species it is these 
features of adaptation which are the last to appear. 
If the history of the individual is an epitome of the 
history of the group to which the individual belongs, 
then adaptive characters appearing late in the growth 
of the individual must have appeared late in the his- 
tory of the group. They are the last changes made 
in the organism—mere after-thoughts in the work of 
creation. 
Crossing the 
barriers. 
