When I have written about the extreme slowness of Natural Selection (296/3.

Mr.Wallace makes a calculation based on Allen's results as to the very short period in which the formation of a race of birds differing 10 to 20 per cent.

from the average in length of wing and strength of beak might conceivably be effected.

He thinks that the slowness of the action of Natural Selection really depends on the slowness of the changes naturally occurring in the physical conditions, etc.) (in which I hope I may be wrong), I have chiefly had in my mind the effects of intercrossing.

I subscribe to almost everything you say excepting the last short sentence.