292 THE PRINCIPLES OF Part II. 



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 



