[11r]

(116G) Birds

supervened or characters are developed, & their transmission to one & the same sex, or to both sexes. To remind the reader I may give as an instance the crest of the peafowl which is developed early in life & is transmitted almost equally to both sexes, whilst the splendid train is developed much later in life & is transmitted to the male alone. So with the common duck the bright wing-speculum is developed early in life & is transmitted to both sexes, whilst the curled tail-feathers follow the same rule of transmission as the train of the peacock.

With respect to variations in colour bird occurring at different ages, if we compare the several breeds, for instance, of the fowl, we shall clearly see that variations do occur very early or late in life & are regularly transmitted to the offspring at corresponding ages. Now if the young male of the wild fowl had varied & had acquired a bright red plumage whilst quite young, such brightness would have been of no service to him, & would not have been favoured through sexual selection until the bird was capable of breeding & had to compete with rival males. Consequently it would