21(5 
SEXUAL SELECTION : BIRDS. 
Part ‘ 
beauty (luring many years after they are fully mature » 
this is the case with the train of the peacock, and ^ 1 
tlie crest and plumes of certain herons ; for instance. b 1L ' 
Ardea Ludovicana ; 40 hut it is very doubtful wheth ef 
the continued development of such feathers is tI,e 
lesult of the selection ot successive beneficial variatiou^ 
or merely of continuous growth. Most fishes contm' 1 ^ 
increasing in size, as long as they are in good heah 1 ' 
and have plenty of food ; and a somewhat similar 
may prevail with the plumes of birds. 
Class Y. When the adults of both sexes have a ^ 
tinet winter and summer plumage, whether or not the i 
differs from the female, the young resemble the adult s °J 
both sexes in their winter dress, or much more rarely tn 
their summer dress, or they resemble the females do**’ 
or the young may have an intermediate character ; ° f 
again, they may differ greatly from the adults in h(,t [ 
their seasonal plumages .— The cases in this class » re 
singularly complex; nor is this surprising, as tK f 
depend on inheritance, limited in a greater or l esS 
degree in three different ways, namely by sex, 
and the season of the year. In some cases the m fl1 ' 
viduals of the same species pass through at least W e 
distinct states of plumage. With the species, in > vb ’ C ! 
the male di iters from the female during the sum 1111 '’' 
season alone, or, which is rarer, during both seasons- 
the young generally resemble the females— as " itH 
the so-called goldfinch of North America, and apP 9 ' 
rently with the splendid Maluri of Australia . 42 ^ 
40 Jerdon ‘Birds of India,’ vol. iii. p. 507, on the peacock. A° d °' 
non, ibid. vol. 111 . p. 139, on the Arden. 
pi' 1 
the 
41 For illustrative oases see vo). iv. of Maegillivrav’s ‘ Hist. 
Birds;’ on Tringa, &c„ p. 229, 271; on the Machetes, p. 172; 
Charadnm hatmh, p. 118 ; on the Charadrim pluvialis, p. 0i- 
lor the goldfinch of N. America, Fringilla Mil, Lu>»-> 
