n6 Animal Life and Intelligence. 



one -weaker or smaller than themselves, and, after over- 

 powering it by numbers, to tear it in pieces." Elimination 

 by competition, passing in this way into elimination by 

 battle, would, during hard times,' be increased. None but 

 the best organized and best adapted could hope to escape. 

 There would be no room for neutral variations, which, in 

 the keenness of the struggle, would be relatively disadvan- 

 tageous. Slightly divergent varieties, before kept apart 

 through local segregation, would be brought into com- 

 petition. The weakest would in some cases be eliminated. 

 In other cases, the best-adapted individuals of each variety 

 might survive. If their experiments in intercrossing, 

 should such occur, gave rise to fertile offspring, more 

 vigorous and better adapted than either parent-race, these 

 would survive, and the parent-forms would be eliminated. 

 But if such experiments in intercrossing gave rise to 

 infertile, weakly offspring, these would be eliminated. Thus 

 sterility between species would become fixed. Wherever, 

 during the preceding good times, divergence had taken 

 place in two different directions of adaptation, and some 

 intermediate forms, fairly good in both directions, had been 

 able to escape elimination, the chances are that these inter- 

 mediates would be in hard times eliminated, and the 

 divergent forms left in possession of the field. Wherever, 

 during good times, a species had acquired or retained a 

 habit of flexibility, that habit would stand it in good stead 

 in the midst of the changes wrought by hard times ; but 

 when it had, on the other hand, acquired rigidity (like the 

 proverbially " inflexible goose "), it would be at a disadvan- 

 tage in the stress of a heightened elimination. 



The alternation of good times and hard times may be 

 illustrated by an example taken from human life. The 

 introduction of ostrich-farming in South Africa brought 

 good times to farmers. Whereupon there followed diver- 

 gence in two directions. Some devoted increased profits to 

 improvements upon their farms, to irrigation works which 

 could not before be afforded, and so forth. For others in- 

 creased income meant increased expenditure and an easier, 



