232 THE DESCENT OF MAN. 



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, rela- 

 tively to their period of development, only in species in a natural 

 state; we will now turn to domesticated animals, and first toucti 

 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 color-blindness — yet these pe- 

 culiarities, and other similar ones, are often limited in their trans- 

 mission to one sex; so that the rule that characters, developed at 

 an early period, tend to be transmitted to both se.^es, 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 lim- 

 ited diseases, we know too little of the period at which they orig- 

 inate, to draw any safe conclusion. Gout, however, seems to fall 

 under our rule, for it is generally caused by intemperance during 

 manhood, and is transmitted from the father to his sons in a 

 much more marked manner than to his daughters. 



In the various domestic breeds of sheep, goats, and cattle, the 

 males differ from their respective females in the shape or develop- 

 ment of their horns, forehead, mane, dewlap, tail, and hump on 

 the shoulders; and these peculiarities, in accordance with our 

 rule, are not fully developed antil a rather late period of life. 

 The sexes of dogs do not differ, except that in certain breeds, 

 especially in the Scotch deer-hound, the male is much larger 

 and heavier than the female; and, as we shall see in a future 

 chapter, the male goes on increasing in size to an unusually late 

 period of life, which, according to rule, will account for his in- 

 creased size being transmitted to his male offspring alone. On 

 the other hand, the tortoise-shell color, which is confined to 

 female cats. Is quite distinct at birth, and this case violates the 

 rule. There is a breed of pigeons in which the males alone are 

 streaked with black, and the streaks can be detected even in the 

 nestlings; but they become more conspicuous at each successive 

 moult, so that this case partly opposes and partly supports the 

 rule. With the English Carrier and Pouter pigeons, the full de- 

 velopment of the wattle and the crop occurs rather late in life, 

 and conformably with the rule, these characters are transmitted 

 in full perfection to the males alone. The following cases perhaps 

 come within the class previously alluded to, in which both sexes 

 have varied in the same manner at a rather late period of life. 



