AS THE BIOLOGIST SEES IT 



kinds for food, space, and opportunity to 

 increase; 



2. An intra-species struggle, or lethal 

 competition among the individuals of a 

 single species, resultant on the over- 

 production due to natural multiplication 

 by geometric progression; and 



3. The constant struggle of individuals 

 and species against the rigors of climate, 

 the danger of storm, flood, drought, cold, 

 and heat. 



Now any animal kind and its individ- 

 uals may be continually exposed to all of 

 these phases of the struggle for existence, 

 or, on the other hand, any one or more 

 of these phases may be largely amelio- 

 rated or even abolished for a given species 

 and its individuals. This amelioration 

 may come about through a happy acci- 

 dent of time or place, or because of the 

 adoption by the species of a habit or mode 

 of life that continually protects it from 

 a certain phase of the struggle. 



For example, the voluntary or involun- 

 tary migration of representatives of a 

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