172 TERRITORY AND REPRODUCTION 



to be too many of this sex or too few of that. 

 And as the power of locomotion increased 

 and the distribution of the sexes became more 

 and more irregular, so the opportunity would 

 be afforded for the development of any variation 

 which would have tended to facilitate the 

 process of pairing, and by so doing have con- 

 ferred upon the individuals possessing it, some 

 slight advantage over their fellows. 



What would have been the most likely 

 direction for variation to have taken ? Any 

 restriction upon the freedom of movement of 

 both sexes would only have added to the 

 difficulties of mating ; but if restriction had 

 been imposed upon one sex, whilst the other 

 had been left free to wander, some order would 

 have been introduced into the process. That 

 the territory serves to restrict the movements 

 of the males and to distribute them uniformly 

 throughout all suitable localities, there can be 

 no question ; and since the instinctive behaviour 

 in relation to it is timed to appear at a very 

 early stage in the seasonal sexual process, the 

 males are in a position to receive mates before 

 the impulse to mate begins to assert itself 

 in the female. 



We will take the Ruff as an example. 

 According to Mr Edmund Selous, pairing, in 

 this species, is promiscuous — the Ruffs are 

 polygamous, the Reeves polyandrous. Suppose, 

 then, that upon this island of some few 

 miles in circumference, whereon his investiga- 

 tions were made, the movements of neither RufF 



