36 ON THE TENDENCY OF VARIETIES TO DEPART 
irruption of some new carnivorous animal seeking 
“ pastures new ”—any change in fact tending to 
render existence more difficult to the species in 
question, and tasking its utmost powers to avoid 
complete extermination; it is evident that, of all 
the individuals composing the species, those forming 
the least numerous and most feebly organized 
variety would suffer first, and, were the pressure 
severe, must soon become extinct. The same causes 
continuing in action, the parent species would next 
suffer, would gradually diminish in numbers, and 
with a recurrence of similar unfavourable conditions 
might also become extinct. The superior variety 
would then alone remain, and on ‘a return to 
favourable circumstances would rapidly increase in 
numbers and occupy the place of the extinct species 
and variety. 
Superior Varieties will ultimately Extirpate the original 
Species. 
The variety would now have replaced the species, 
of which it would be a more perfectly developed 
and more highly organized form. It would be in 
all respects better adapted to secure its safety, and 
to prolong its individual existence and that of the 
race. Such a variety could not return to the ori- 
ginal form; for that form is an inferior one, and 
could never compete with it for existence. Granted, 
therefore, a “tendency ” to reproduce the original 
type of the species, still the variety must ever re- 
