SEXUAL SELECTION 601 



"We may now consider the classes of cases under which 

 the differences and resemblances between the plamage of 

 the young and the old, in both sexes, or in one sex alone, 

 may be grouped. Rules of this kind were first enounced 

 by Cuvier; but with the progress of knowledge they re- 

 quire some modification and amplification. This I have 

 attempted to do, as far as the extreme complexity of the 

 subject permits, from information derived from various 

 sources ; but a full essay on this subject by some compe- 

 tent ornithologist is much needed. In order to ascertain to 

 what extent each rule prevails, I have tabulated the facts 

 given in four great works, namely, by Macgillivray on the 

 birds of Britain, Audubon on those of North America, Jer- 

 don on those of India, and Gould on those of Australia. I 

 may here premise, first, that the several cases or rules grad- 

 uate into each other; and, secondly, that when the young 

 are said to resemble their parents, it is not meant that they 

 are identically alike, for their colors are almost always less 

 vivid, and the feathers are softer and often of a different 

 shape. 



EULES OR CLASSES OF CASES 



I. When the adult male is more beautiful or conspicu- 

 ous than the adult female, the young of both sexes in their 

 first plumage closely resemble the adult female, as with the 

 common fowl and peacock ; or, as occasionally occurs, they 

 resemble her much more closely than they do the adult male. 



II. When the adult female is more conspicuous than the 

 adult male, as sometimes though rarely occurs, the young of 

 both sexes in their first plumage resemble the adult male. 



III. When the adult male resembles the adult female, 

 the young of both sexes have a peculiar first plumage of 

 their own, as with the robin. 



IV. When the adult male resembles the adult female, 

 the young of both sexes in their first plumage resemble the 

 adults, as with the kingfisher, many parrots, crows, hedge- 

 warblers 



