THE YOUNG LIKE BOTH ADULTS. 
213 
xvi. 
<Jt *' sexes is perhaps the most probable. I may here 
'* that 1 have endeavoured, with little success, bv 
^‘suiting various works, to decide how far with birds 
16 period of variation has generally determined the 
'Emission of characters to one sex or to both. The 
v ° rules, often referred to (namely, that variations 
° c currinor late in life are transmitted to one and the 
Sa «ie 
sex, whilst those which occur early in life are 
|' a nsmitted to both sexes), apparently hold good 
in 
first, 34 second, and fourth classes of cases; but 
lf ' 6 y fail in an equal number, namely, in the third, 
in the fifth, 35 and iu the sixth small class, 
'ey hold good, however, as far as I can judge, with a 
e °Hsiderable majority of the species of birds. Whether 
° r Hot this be so, we may conclude from the facts 
j' lv ° n in the eighth chapter that the period of variation 
j, i,s been one important element in determining the 
0l 'ii of transmission. 
^ ith birds it is difficult to decide by what standard 
Vi,; ought to judge of the earliness or lateness of the 
j/'iod of variation, whether by the age in reference to 
110 duration of life, or to the power of reproduction, 
01 to the number of moults through which the species 
Passes. The moulting of birds, even within the same 
Hinily, sometimes differs much without any assignable 
t[ , instance, tlie males of Tanagra estiva and Fringilla cyanea 
^ three years, the male of Fringilla ciris four years, to complete 
|, beautiful plumage. (See Audubon, ‘Ornith. Biography,’ vol. i. 
j,j 280, 378.) Tlie Harlequin duck takes three years (ibid. vol. 
J.,/ 1 ' ^t4). The male of the Gold pheasant, as I hear from Mr. J. 
kio'if 1 can he distinguished from the female when about three 
of ti 18 oll b Hut He does not acquire his full splendour until the end 
:i5 '® September in the following year, 
pi jhus the Ibis tantalus and Grus Ameriuanus take four years, the 
tp _ Q S° several years, and the Arclea Ludovicana two years, before 
V 0] > . ac< iuire their perfect plumage. See Audubon, ibid. vol. i. p. 221 ; 
' lii - P- 133, 139, 211. 
