We have little evidence on this head, but what we have certainly points the other way; for it is notorious that breeders of cattle, horses and various fancy animals, cannot positively tell, until some time after birth, what will be the merits and demerits of their young animals.

We see this plainly in our own children; we cannot tell whether a child will be tall or short, or what its precise features will be.

The question is not, at what period of life any variation may have been caused, but at what period the effects are displayed.

The cause may have acted, and I believe often has acted, on one or both parents before the act of generation.

It deserves notice that it is of no importance to a very young animal, as long as it is nourished and protected by its parent, whether most of its characters are acquired a little earlier or later in life.