like other constitutional characters, in the first place an individual one, which...may become more or less hereditary, and therefore specific; and thence, but in a very faint degree, generic." He seems to mean to argue against the conclusion which Sir Joseph Hooker had quoted from Mr.Darwin that "species of large genera are more variable than those of small." [On large genera varying, see Letter 53.]) Hooker was convinced by my data, never as yet published in full, only abstracted in the "Origin." Page lxxviii .-- I dispute whether a new race or species is necessarily, or even generally, descended from a single or pair of parents.

The whole body of individuals, I believe, become altered together--like our race-horses, and like all domestic breeds which are changed through "unconscious selection" by man.

(290/3.

Bentham had said: "We must also admit that every race has probably been the offspring of one parent or pair of parents, and consequently originated in one spot." The Duke of Argyll inverts the proposition.) When such great lengths of time are considered as are necessary to change a specific form, I greatly doubt whether more or less rapid powers of multiplication have more than the most insignificant weight.
These powers, I think, are related to greater or less destruction in early life.
Page lxxix .-- I still think you rather underrate the importance of isolation.

I have come to think it very important from various grounds; the anomalous and quasi-extinct forms on islands, etc., etc., etc.
With respect to areas with numerous "individually durable" forms, can it be said that they generally present a "broken" surface with "impassable barriers"?
This, no doubt, is true in certain cases, as Teneriffe.