original cross, or than Carrier with Carrier. Here, you see, is a
physiological contrast between the races produced by selective
modification and natural species. I shall inquire into the value of
this fact, and of some modifying circumstances by and by; for the
present I merely put it broadly before you.

But while considering this question of the limitations of species, a
word must be said about what is called RECURRENCE--the tendency of
races which have been developed by selective breeding from varieties to
return to their primitive type. This is supposed by many to put an
absolute limit to the extent of selective and all other variations.
People say, "It is all very well to talk about producing these
different races, but you know very well that if you turned all these
birds wild, these Pouters, and Carriers, and so on, they would all
return to their primitive stock." This is very commonly assumed to be
a fact, and it is an argument that is commonly brought forward as
conclusive; but if you will take the trouble to inquire into it rather
closely, I think you will find that it is not worth very much. The
first question of course is, Do they thus return to the primitive
stock? And commonly as the thing is assumed and accepted, it is
extremely difficult to get anything like good evidence of it. It is
constantly said, for example, that if domesticated Horses are turned
wild, as they have been in some parts of Asia Minor and South America,
that they return at once to the primitive stock from which they were
bred. But the first answer that you make to this assumption is, to ask
who knows what the primitive stock was; and the second answer is, that
in that case the wild Horses of Asia Minor ought to be exactly like the
wild Horses of South America. If they are both like the same thing,
they ought manifestly to be like each other! The best authorities,
however, tell you that it is quite different. The wild Horse of Asia