EFFECT OF THE GREGARIOUS INSTINCT 295 



vary in the persistency with which they strive 

 to attain their unknown end, and in the direction 

 in which they travel in pursuit of it. So that in 

 each generation they will fall into three classes : 

 (1) those which are inert, (2) those which 

 wander along the line of expansion, (3) those 

 which wander in other directions. If then the 

 struggle for life at this particular juncture in the 

 evolution of the breeding range is a struggle for 

 the means of subsistence, the members of these 

 three classes will not be in a like satisfactory 

 position so far as the competition for food is 

 concerned. Those in the first class — i.e., those 

 in which the activity feelings are weak — will 

 neither gain the benefits which arise from 

 mutual help, nor will they have much prospect 

 of enduring through the season of scarcity. 

 Those in the third class will, it is true, derive 

 some assistance one from another, and so be in 

 a better position to discover what food may be 

 available ; but inasmuch as they will remain in 

 regions where the climate alternates' and the 

 supply of food is liable to fall below the 

 minimum required, the chances are that a high 

 percentage wiU fail in the struggle for existence. 

 We come now to those in the second class, and 

 it is upon them that I wish more particularly to 

 focus attention. The initial movement in their 

 case will be in the direction from which outward 

 expansion has all along taken place. Within a 

 comparatively short distance they will reach 

 districts where the species is plentiful, and here, 

 associating with others that have some traditional 



