Chap. VIII.] SEXUAL SELECTION. 283 



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 peculiarities, and other similar ones, are often limit- 

 ed 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 trans- 

 mitted 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 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 our rule ; for it is gen- 

 erally caused by intemperance after early youth, 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 mules differ from their respective females in 

 the shape or development of their horns, forehead, mane, 

 dewlap, tail, and hump on the shoulders ; and these pecu- 

 liarities, in accordance with our rule, are not fully devel- 

 oped until rather late in life. With dogs, the sexes 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 imusually late 

 period of life, which will account, according to our rule, 

 for his increased size being transmitted to his male off- 

 spring alone. On the other hand, the tortoise-shell color 

 of the hair, which is confined to female cats, is quite dis- 



