90 CRITICISMS ON “THE ORIGIN OF SPECIES” pr 
assumes no special tendency of organisms to give — 
rise to useful varieties, and knows nothing of needs — 
of development, or necessity of perfection. What 
he says is, in substance: All organisms vary. It 
is in the highest degree improbable that any given 
ledeeah baie 
mre ay et 
variety should have exactly the same relations to — 
surrounding conditions as the parent stock. In — 
that case it is either better fitted (when the varia- — 
tion may be called useful), or worse fitted, to cope — 
with them. If better, it will tend to supplant the — 
parent stock ; if worse, it will tend to be extin- : . 
guished by the parent stock. 
If (as is hardly conceivable) the new variety is — 
so perfectly adapted to the conditions that no ~ 
improvement upon it is possible,—it will persist, — 
because, though it does not cease to vary, the | 
varieties will be inferior to itself. 
If, as is more probable, the new variety is by no — 
means perfectly adapted to its conditions, but only 
fairly well adapted to them, it will persist, so long — 
as none of the varieties which it throws off are 
better adapted than itself. 
On the other hand, as soon as it varies in a 
useful way, 7.c. when the variation is such as to — 
adapt it more perfectly to its conditions, the fresh 
variety will tend to supplant the former. 
So far from a gradual progress towards perfection 
forming any necessary part of the Darwinian 
creed, it appears to us that it is perfectly consistent 
with indefinite persistence in one state, or with 
