DIVERGENCE NOT ALWAYS ADVANTAGEOUS. 217 



the snails he has found in similar stations not far distant ; but what is 

 his surprise to find only different species, all allied to, but quite dis- 

 tinct from, those he has previously known ! Twenty miles from the 

 first valley he renews his investigations, finding the forms of all the 

 different groups still more divergent, though all the conditions of the 

 environment are, so far as he can observe, the same. 



He finally perceives that he must give up the theory that the cause 

 of this divergence is exposure to different environments. 



(3) When the environment is the same in two districts occupied by 

 allied species or varieties, it is evident that the differences that distinguish 

 the latter can not be advantageous, even though their differences include 

 strongly contrasted habits. For in order that these differences should 

 be advantageous, it is necessary not only that they should relate to 

 the performance of vital functions, and, therefore, be differences of 

 adaptation, but it is necessary that these differences of adaptation 

 should relate to differences in the environment, so that the forms 

 would be at some disadvantage if they should exchange districts. 

 Advantageous differences are always adaptational ; but adaptational 

 differences are not always advantageous, and in such cases the diver- 

 gence can not be primarily attributed to diversity in the action of 

 natural selection in the different districts. Under the protection of 

 isolation, diversity of selection may arise which helps in producing 

 divergence ; but when the environments are the same, the divergence 

 is in no sense advantageous ; for, if a given combination of characters 

 is an advantage in one district, so would it also be in the other dis- 

 trict, and the difference or divergence is no advantage. 



A familiar example will perhaps put the distinction between the 

 causes of survival and transformation and the causes of divergent sur- 

 vival and transformation in a clearer light. The forms of language 

 are growths that are governed by the laws of utility as fully as the 

 forms of varieties and species. Each language and each part of a 

 language exists and persists only as it is found to be of use. The ' ' sur- 

 vival of the fittest" is a law that is perhaps as conspicuous in the 

 domain of language as in the organic world. Again, every language, 

 like every organic species, is in many respects determined by the 

 environment. A language, for example, developed in Java will pre- 

 sent names for many plants and animals that will not be represented 

 in a language developed in Greenland. But, granting all this, does it 

 follow that linguistic differences are necessarily advantageous? The 

 Polynesian system of counting by fours, and the Eskimo system that 

 proceeds by scores, are undoubtedly useful systems; but is there any- 

 thing advantageous in the diff erence ? I think not, for each system is 



