Chap. XVI. THE YOUNG LIKE BOTH ADULTS. 
209 
acquired through sexual selection by the nearly mature 
males ; but that, differently from what occurs in the 
two first classes, the transmission, though limited to the 
same age, has not been limited to the same sex. Conse- 
quently both sexes when mature resemble each other 
and differ from the young. 
Class IY. When the adult male resemlles the adult 
female^ the young of both sexes in their first plumage 
resemble the adults, — In this class the young and the 
adults of both sexes, whether brilliantly or obscurely 
coloured, resemble each other. Such cases are, I think, 
more common than those in the last class. Y^e have 
in England instances in the kingfisher, some wood- 
peckers, the jay, magpie, crow, and many small dull- 
coloured birds, such as the hedge-warbler or kitty- wren. 
But the similarity in plumage between the young and 
the old is never absolutely complete, and graduates away 
into dissimilarity. Thus the young of some members of 
the kingfisher family are not only less vividly coloured 
than the adults, but many of the feathers on the lower 
surface are edged with brown,^'^ — a vestige probably of 
a former state of the plumage. Frequently in the same 
group of birds, even within the same genus, for instance 
in an Australian genus of parrokeets (Platycercus), the 
young of some species closely resemble, whilst the 
young of other species differ considerably from their 
parents of both sexes, which are alike.^^ Both sexes 
and the young of the common jay are closely similar; 
but in the Canada jay {Perisoreus canadensis) the young 
differ so much from their parents that they were formerly 
described as distinct species.^^ 
Jerdon, ^ Birds of India,’ vol. i. p. 222, 228. Gould’s ‘ Handbook 
of the Birds of Australia,’ vol. i. 124, 130. 
28 Gould, Ibid. vol. ii. p. 37, 46, 56. 
29 Audubon, ‘ Ornith. Biography,’ vol. ii. p. 55, 
VOL. II. 
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