166r

Ch. 4

(4

Mainly, though not exclusively, though the arts, which are the products of the intellect. It is, therefore, so obvious that the intellectual powers are of the highest importance to man, & it is clear that they might be advanced through natural selection, aided by the inherited effect of use or habit on the brain, that it seems to me superfluous to enter in detail on [words excised] steps by which

[Descent, pp. 35-6: "With respect to animals very low in the scale, I shall have to give some additional facts under Sexual Selection, shewing that their mental powers are higher than [p. 36:] might have been expected. The variability of the faculties in the individuals of the same species is an important point for us, and some few illustrations will here be given. But it would be superfluous to enter into many details on this head, for I have found on frequent enquiry, that it is the unanimous opinion of all those who have long attended to animals of many kinds, including birds, that the individuals differ greatly in every mental characteristic."]