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THE PRINCIPLES OF 
Part IL 
of the same species of butterfly, in which certain coloured 
marks are confined to one sex, whilst other marks are 
common to both sexes. A difference of this kind in the 
period of development is not so improbable as it may 
at first appear ; for with the Orthoptera, which assume 
their adult state, not by a single metamorphosis, but by 
a succession of moults, the young males of some species 
at first resemble the females, and acquire their distinc- 
tive masculine characters only during a later moult. 
Strictly analogous cases occur during the successive 
moults of certain male crustaceans. 
We have as yet only considered the transference of 
characters, relatively to their period of development, with 
species in a natural state ; we will now turn to domes- 
ticated animals; first touching on monstrosities and 
diseases. The presence of supernumerary digits, and 
the absence of certain phalanges, must be determined 
at an early embryonic period* — the tendency to profuse 
bleeding is at least congenital, as is probably colour- 
blindness — yet these peculiarities, and other similar 
ones, are often limited in their transmission to one sex ; 
so that the rule that characters which are developed 
at an early period tend to be transmitted to both sexes,, 
here wholly fails. But this rule, as before remarked,, 
does not appear to be nearly so generally true as the 
converse proposition, namely, that characters which 
appear late in life in one sex are transmitted exclu- 
sively to the same sex. From the fact of the above 
abnormal peculiarities becoming attached to one sex, 
long before the sexual functions are active, we may 
infer that there must be a difference of some kind 
between the sexes at an extremely early age. With 
respect to sexually-limited diseases, we know too little 
of the period at which they originate, to draw any 
fair conclusion. Gout, however, seems to fall under 
