240 DARWINISM STATED BY DARWIN HIMSELF. 



it is diflftcult to understand why tte males of species, 

 of which the progenitors were primordially free, should 

 invariably have acquired the habit of approaching the 

 females, instead of being approached by them. But, in 

 all cases, in order that the males should seek efficiently, 

 it would be necessary that they should be endowed with 

 strong passions; and the acquirement of such passions 

 would naturally follow from the more eager leaving a 

 larger number of offspring than the less eager. 



TRANSMISSION OF SEXUAL CHARACTEKISTICS. 



Why certain characters should be inherited 

 ° ' by both sexes, and other characters by one sex 

 alone, namely, by that sex in which the character first ap- 

 peared, is in most cases quite unknown. We can not even 

 conjecture why, with certain sub-breeds of the pigeon, 

 black strise, though transmitted through the female, 

 should be developed in the male alone, while every other 

 character is equally transferred to both sexes. Why, 

 again, with cats, the tortoise-shell color should, with rare 

 exceptions, be developed in the female alone. The very 

 same character, such as deficient or supernumerary digits, 

 color-blindness, etc., may with mankind be inherited by 

 the males alone of one family, and in another family by 

 the females alone, though in both cases transmitted 

 through the opposite as, well as through the same sex. 

 Although we are thus ignorant, the two following rules 

 seem often to hold good : that variations which first ap- 

 pear in either sex at a late period of life tend to be de- 

 veloped in the same sex alone ; while variations which 

 first appear early in life in either sex tend to be devel- 

 oped in both sexes. I am, however, far from supposing 

 that this is the sole determining causCi 



