and ix.): they remind me of Forbes' bad term of Polarity.

(80/3.

Forbes, "On the Manifestation of Polarity in the Distribution of Organised Beings in Time."-- "R.

Institution Proc." I., 1851-54.) I daresay selection by man would generally work quicker than Natural Selection; but the important distinction between them is, that man can scarcely select except external and visible characters, and secondly, he selects for his own good; whereas under nature, characters of all kinds are selected exclusively for each creature's own good, and are well exercised; but you will find all this in Chapter IV.
Although the hound, greyhound, and bull-dog may possibly have descended from three distinct stocks, I am convinced that their present great amount of difference is mainly due to the same causes which have made the breeds of pigeons so different from each other, though these breeds of pigeons have all descended from one wild stock; so that the Pallasian doctrine I look at as but of quite secondary importance.
In my bigger book I have explained my meaning fully; whether I have in the Abstract I cannot remember.
LETTER 81.

TO C.LYELL.