The greater variability of the female sex is new to me.

Your Guiana case seems in some degree analogous, as far as plants are concerned, with the modern plains of La Plata, which seem to have been colonised from the north, but the species have been hardly modified.

(122/2.

Mr.Bates (page 349) gives reason to believe that the Guiana region should be considered "a perfectly independent province," and that it has formed a centre "whence radiated the species which now people the low lands on its borders.") Would you kindly answer me two or three questions if in your power?
When species A becomes modified in another region into a well-marked form C, but is connected with it by one (or more) gradational forms B inhabiting an intermediate region; does this form B generally exist in equal numbers with A and C, OR INHABIT AN EQUALLY LARGE AREA?
The probability is that you cannot answer this question, though one of your cases seems to bear on it...
You will, I think, be glad to hear that I now often hear of naturalists accepting my views more or less fully; but some are curiously cautious in running the risk of any small odium in expressing their belief.
LETTER 123.

TO H.W.BATES.