SUPPLEMENTAL NOTE. 713 



somest or the most attractive in any manner to the females 

 would pair oftenest, and would leave rather more offspring 

 than other males. The offspring of the former, although 

 variously intercrossed, would either inherit the peculiarities 

 of their fathers or transmit an increased tendency to vary 

 in the same manner. Consequently the whole body of 

 males inhabiting the same country would tend from the 

 effects of constant intercrossing to become modified almost 

 uniformly, but sometimes a little more in one character and 

 sometimes in another, though at an extremely slow rate; all 

 ultimately being thus rendered more attractive to the 

 females. The process is like that which I have called 

 unconscious selection by man, and of which I have given 

 several instances. In one country the inhabitants value a 

 fleet or light dog or horse, and in another country a heavier 

 and more powerful one; in neither country is there any 

 selection of individual animals with lighter or stronger 

 bodies and limbs; nevertheless, after a considerable lapse 

 of time, the individuals are found to have been modified in 

 the desired manner almost uniformly, though differently in 

 each country. In two absolutely distinct countries inhab- 

 ited by the same species, the individuals of which can 

 never, during long ages, have intermigrated and inter- 

 crossed, and where, moreover, the variations will probably 

 not have been identically the same, sexual selection might 

 cause the males to differ. Nor does the belief appear to 

 me altogether fanciful that two sets of females, surrounded 

 by a very different environment, would be apt to acquire 

 somewhat different tastes with respect to form, sound or 

 color. However this may be, I have given in my '^ Descent 

 of Man" instances of closely allied birds inhabiting dis- 

 tinct countries, of which the young and the females cannot 

 be distinguished, while the adult males differ considerably, 

 and this may be attributed with much probability to the 

 action of sexual selection. 



