Page:The Zoologist, 4th series, vol 2 (1898).djvu/434

402 only birds which have been observed to turn black from feeding on hemp-seed, nor is hemp-seed the only seed which conduces to such a change of colour. Larks have been known to become black after being fed for some time on hemp-seed; and the late Mr. Blyth informed us that he had seen one of the little Amandavat Finches which had become black, though fed entirely on canary-seed." Again, there is the "change produced in so many of the Green Parrots by the native peoples of Guiana, who, by feeding these birds on a special diet, consisting largely of pounded corn or maize, produce eventually yellow-coloured birds." A pair of American Screech Owls (Megascops asio) which were fed in captivity largely on liver, and which were originally in typical grey plumage, exhibited subsequently, especially in the larger female Owl, an actual change from grey to redbrown in individual feathers, and the red phase was not thought entirely, if at all, due to new feather-growth. By mixing madder with the food of a female mammal, Flourens produced a red colour in the bones of the foetus. By placing the eggs of a Salmon Trout in waters which only nourished White Trout, Coste noticed the eggs became gradually paler, and produced Trout which had lost the characteristic colour of their race. "If a Horse has an addition of arsenic to its usual food, its hair becomes more glossy; and Holmegreen has proved that if Pigeons are fed with meat they change not only the colours of their feathers, but also their odour." In the Salmonoids the flesh is frequently of a marked pinkish hue, "brought about by the crustaceans on which these carnivorous fishes so largely feed." By changing or varying the food of lepidopterous larvse, much variation has been produced in the depth of colour of the imagines.

The whole problem of the colouration of mankind centres largely on the question of what was the tint or hue of the skin of