Chap. XXI. 
AND CONCLUDING KEMAKKS. 
397 
with mammals, birds, reptiles, fishes, insects, and even 
crustaceans, the differences between the sexes follow 
almost exactly the same rules. The males are almost 
always the wooers ; and they alone are armed with spe- 
cial weapons for fighting with their rivals. They are 
generally stronger and larger than the females, and are 
endowed with the requisite qualities of courage and pug- 
nacity. They are provided, either exclusively or in a 
much higher degree than the females, with organs for 
producing vocal or instrumental music, and with odori- 
ferous glands. They are ornamented with infinitely 
diversified appendages, and with the most brilliant or 
conspicuous colours, often arranged in elegant patterns, 
whilst the females are left unadorned. When the sexes 
differ in more important structures, it is the male which 
is provided with special sense-organs for discovering the 
female, with locomotive organs for reaching her, and 
often with prehensile organs for holding her. These 
various structures for securing or charming the female 
are often developed in the male during only part of the 
year, namely the breeding season. They have in many 
cases been transferred in a greater or less degree to 
the females ; and in the latter case they appear in 
her as mere rudiments. They are lost by the males 
after emasculation. Grenerally they are not developed 
in the male during early youth, but appear a short 
time before the age for reproduction. Hence in most 
cases the young of both sexes resemble each other ; 
and the female resembles her young offspring through- 
out life. In almost every great class a few anomalous 
cases occur in which there has been an almost complete 
transposition of the characters proper to the two sexes ; 
the females assuming characters which properly belong 
to the males. This surprising uniformity in the laws 
regulating the differences between the sexes in so many 
