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112 NATURAL SELECTION vwhen fabricating their nest. They had no standard to workby, no nests of their own kind to copy, no older birds to givethem any instruction, and the result is the abnormal structureI have just described. Perhaps these chaffinches imitated insome degree the nest of some New Zealand species ;or itmay be that the few resemblances to the typical nest of thePalsearctic chaffinch are the results of memory the dimremembrance of the nest in which they had been reared, butwhich had almost been effaced by novel surroundings andchanged conditions of life. Any way we have here, at least,a most interesting and convincing proof that birds do notmake their nests by blind instinct, but by imitating the nestin which they were reared, aided largely by rudimentaryreason and by memory." lThis experiment also leaves much to be desired, but itundoubtedly shows that instinct alone does not determinethe form and structure of a bird's nest, or we should not seeso great a departure from the type in the case of the NewZealand chaffinches.The Skill exhibited in Nest-building ExaggeratedWe are too apt to assume that because a nest appears tous delicately and artfully built, it therefore requires muchspecial knowledge and acquired skill (or their substitute,instinct) in the bird who builds We it. forget that it isformed twig by twig and fibre by fibre, rudely enough at first,but crevices and irregularities, which must seem huge gapsand chasms in tiie eyes of the little builders, are filled up bytwigs and stalks pushed in by slender beak and active foot,and that the wool, feathers, or horsehair are laid thread bythread, so that the result seems a marvel of ingenuity to us,just as would the rudest Indian hut to a native of Brobdignag.Levaillant has given an account of the process of nestbuildingby a little African warbler, which sufficiently showsthat a very beautiful structure may be produced with verylittle art. The foundation was laid of moss and flax interwovenwith grass and tufts of cotton, and presented a rudemass, five or six inches in diameter, and four inches thick.This was pressed and trampled down repeatedly, so as at last1 Nature, voL xxxi. p. 533 (April 1885).