78 STRUGGLE FOR EXISTENCE. Chap. III. 



into slightly hotter or colder, damper or drier districts. 

 In this case we can clearly see that if we wished in 

 imagination to give the plant the power of increasing 

 in number, we should have to give it some advantage 

 over its competitors, or over the animals which preyed 

 on it. On the confines of its geographical range, a change 

 of constitution with respect to climate would clearly 

 be an advantage to our plant; but we have reason 

 to believe that only a few plants or animals range so 

 far, that they are destroyed by the rigour of the climate 

 alone. Not until we reach the extreme confines of life, 

 in the arctic regions or on the borders of an utter desert, 

 will competition cease. The land may be extremely 

 cold or dry, yet there will be competition between some 

 few species, or between the individuals of the same 

 species, for the warmest or dampest spots. 



Hence, also, we can see that when a plant or animal 

 is placed in a new country amongst new competitors, 

 though the climate may be exactly the same as in its 

 former home, yet the conditions of its life will generally 

 be changed in an essential manner. If we wished to in- 

 crease its average numbers in its new home, we should 

 have to modify it in a different way to what we should 

 have done in its native country ; for we should have to 

 give it some advantage over a different set of com- 

 petitors or enemies. 



It is good thus to try in our imagination to give any 

 form some advantage over another. Probably in no 

 single instance should we know what to do, so as to 

 succeed. It will convince us of our ignorance on the 

 mutual relations of all organic beings ; a conviction as 

 necessary, as it seems to be difficult to acquire. All 

 that we can do, is to keep steadily in mind that each 

 organic being is striving to increase at a geometrical 



