34§ 
It follows, then, from what has been said, that the 
principle of correlated variation obtains in nature ; that 
it will act, whatever cause produces the initial modification 
in one part ; that Natural Selection cannot act in con 
nection with this principle ; and that neither Natural 
Selection nor Sexual Selection can of itself evolve 
results similar to those produced by correlated variation. 
We have, then, in the principle we are considering, a very 
powerful agent in the transmutation of species ; but one 
which affords no reason for supposing that the transmu 
tation of one structure of correlated parts into another 
structure of parts differently correlated can be brought 
about through the action of Natural Selection.