4.86 The Descent of Man. Part I i. 



resemble the adults, firstly, in their winter dress ; secondly, and this ia 

 of much rarer occurrence, in their summer dreos ; thirdly, they may be 

 intermediate between these two states; and, fourthly, they may differ 

 greatly from the adults at all seasons. We have an instance of the 

 first of these four casts in one of the egrets of India (Buphus coru- 

 mandus), in which the young and the adults of both sexes are white 

 during the winter, the adults becoming golden-buff during the summer. 

 With the gaper (Anastomus oscitans) of India we have a similar case, 

 but the colours are reversed: for the young and the adults of both 

 sexes are grey and black during the winter, the adults becoming white 

 during the summer. 43 As an instance of the second case, the young of 

 the razor-bill (Alca torda, Linn.), in an early state of plumage, are 

 coloured like the adults during the summer ; and the young of the 

 white-crowned sparrow of North America (Fringilla leucnphnjs), as soon 

 as fledged, have elegant white stripes on their heads, which are lost by 

 the young and the old during the winter. 44 With respect to the third 

 case, namely, that of the young having an intermediate character between 

 the summer and winter adult plumages, Yariell 45 insists that this 

 occurs with many waders. Lastly, in regard to the young differing 

 greatly from botii sexes in their adult summer and winter plumages, 

 this occurs with some herons and egrets of North America and India,— 

 the young alone being white. 



I will make only a few remarks on these complicated cases. When 

 the young resemble the females in their summer dress, or the adults of 

 both sexes in their winter dress, the cases difftr from those given under 

 Classes I. and III. only in the characters originally acquired by the 

 males during the breeding-season, having been limited in their trans- 

 mission to the corresponding season. When the adults have a distinct 

 summer and winter plumage, and the young differ from both, the case 

 is more difficult to understand. We may admit as probable that the 

 young have retained an ancient state of plumage ; we can account by 

 sexual selection for the summer or nuptial plumage of the adults, but 

 I low are we to account for their distinct winter plumage? If we couid 

 admit that this plumage serves in all cases as a protection, its ac- 

 quirement would be a simple affair; but there seems no good reason 

 for this admission. It may be suggested that the widely different 

 conditions of life during the winter and summer have acted in a direct 

 manner on the plumage; this may have had some effect, but I have 

 not much confidence in so great a difference as we sometimes see 

 between the two plumages, having been thus caused. A more probable 

 explanation is, that an ancient style of plumage, partially modified 

 through the transference of some characters from the summer plumage, 

 has been retained by the adults during the winter. Finally, all the 

 cases in our present class apparently depend on characters acquired by 

 the adult males, having been variously limited in their transmission 

 according to age, season, and sex; but it would not he worth while to 

 attempt to follow out these complex relations. 



43 I am indebted to Mr. Blyth On the Fringilla leucophr^s, Au- 

 for information as to the Buphus ; ,dubon, ibid. vol. ii. p. 89. I shall 

 gee also Jerdoa, 'Birds of India,' have hereafter to refer to the young 

 vol. iii. p. 749. On the Anastomus, of certain herons and egrets beins? 

 see Blyth, in * Ibis,' 1867, p. 173. white. 



44 On the Alca, see Macgillivray, 45 ' History of British Birds,' vol 

 Hist. Brit. Birds,' vol. v. p. 347. i. 1839, p. 159. 



