254 
THE PRINCIPLES OP 
Part II. 
we confine the term "primary” to the reproductive 
glands, it is scarcely possible to decide, as far as the 
organs of prehension are concerned, which ought to 
be called primary and which secondary. 
The female often differs from the male in haying 
organs for the nourishment or protection of her young, 
as the mammary glands of mammals, and the ab- 
dominal sacks of the marsupials. The male, also, in 
some few cases differs from the female in possessing 
analogous organs, as the receptacles for the ova pos- 
sessed by the males of certain fishes, and those tem- 
porarily developed in certain male frogs. Female bees 
have a special apparatus for collecting and carrying 
pollen, and their ovipositor is modified into a sting for 
the defence of their larvae and the community. In the 
females of many insects the ovipositor is modified in 
the most complex manner for the safe placing of the 
eggs. Numerous similar cases could be given, but they 
do not here concern us. There are, however, other 
sexual differences quite disconnected with the primary 
organs with which we are more especially concerned- 
such as the greater size, strength, and pugnacity of the 
male, his weapons of offence or means of defence 
against rivals, his gaudy colouring and various orna- 
ments, his power of song, and other such characters. 
Besides the foregoing primary and secondary sexual 
differences, the male and female sometimes differ in 
structures connected with different habits of life, and 
not at all, or only indirectly, related to the reproductive 
functions. Thus the females of certain flies (Culicidse 
and Tabanidse) are blood-suckers, whilst the males live 
on flowers and have their mouths destitute of man- 
dibles . 1 The males alone of certain moths and of some 
1 Westwood, ‘Modern Class, of Insects/ vol. ii. 1810, p. 541. In 
