XVIII THE PROBLEM OF UTILITY 397 



overlap, or very slightly so, then we have the condition pre- 

 cedent to the formation of a species by the extinction of 

 the type, thus leaving the variety to represent the species. 

 Of course in this case we do not know that the characters 

 which distinguish the variety are useless ; but if they are 

 so, and if the variety should possess some superior vigour 

 of constitution or other useful peculiarity which enables 

 it to survive when the type dies out, we should have an 

 illustration of one mode in which useless specific characters 

 may possibly have arisen. 



The inquiry is interesting, however, because it brings 

 to light the rather unexpected fact, that fixed varieties of 

 plants occupying considerable areas to the exclusion of 

 the type are not common, and, perhaps, in our island do 

 not exist. And should they be found to occur more 

 frequently in other countries — as varieties of birds, 

 mammals, and reptiles do occur in separate areas in North 

 America they may be usually explained as adaptations 

 to very different climatic conditions, in which case the 

 distinguishing characters will be utilitarian, and the local 

 varieties will be really incipient species. 



Conclusions from the Inquiry. 



The preceding inquiry leads us to certain very definite 

 conclusions. In the first place, we see that species, which 

 have been differentiated as such by the laws of variation 

 and survival of the fittest, must be characterized by 

 certain peculiarities whereby they have obtained an 

 advantage in the struggle with their fellows. These 

 peculiarities constitute their " specific characters," and 

 these must be useful. As this applies also to every 

 species in the direct line of descent, the characters which 

 are sectional or generic must also, at the time of their 

 origin, have been useful. 



In the second place, although non-utilitarian characters 

 do undoubtedly appear in the normal course of variation, 

 no agency has yet been detected adequate to the extension 

 of these useless peculiarities to all the individuals which 

 constitute a species, and, further, to prevent their 



