268 THE DESCENT OF MAN. 



one^ could be given, in which the characters follow our two 

 rules in their order of development. 



As most insects emerge from the pupal state in a mature 

 condition it is doubtful whether the period of development 

 can determine the transference of their characters to one or 

 to both sexes. But we do not know that the colored scales, 

 for instance, in two species of butterflies, in one of which 

 the sexes differ in color, while in the other they are alike, 

 are developed at the same relative age in. the cocoon. Nor 

 do we know whether all the scales are simultaneously devel- 

 oped on the wings of the same species of butterfly, in 

 which certain colored marks are confined to one sex, while 

 others 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 suc- 

 cession of moults, the young males of some species at first 

 resemble the females, and acquire their distinctive mascu- 

 line characters only at a later moult. Strictly analogous 

 cases occur at the successive moults of certain male 

 crustaceans. 



We have as yet considered the transference of characters, 

 relatively to their period of development, only in species in 

 a natural state; we will now turn to domesticated animals, 

 and first touch 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 con- 

 genital, as is probably color-blindness yet these peculiar- 

 ities, and other similar ones, are often limited in their 

 transmission to one sex; so that the rule that characters, 

 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 general as the converse one, 

 namely, that characters which appear late in life in one sex 

 are transmitted exclusively 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 some difference 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 safe conclusion. Gout, however, 

 se(nns to fall under our rule, for it is generally caused by 



