^9D STUDIES, SCIENTIFIC AND SOCIAL chap- 



cally the same laws and processes as are adequate to 

 produce the different species of Rubus or of Canis, from 

 some ancestral bramble or dog respectively, his opponents 

 have undoubtedly a case well worthy of being argued out 

 in the courts of science. They should, however, remember 

 that no final judgment has been given or can be given 

 while the evidence on both sides is not only circumstantial 

 but imperfect and contradictory ; and it would be well not 

 to declare too confidently that Mr. Darwin's theory has 

 hopelessly broken down, since a majority both of naturalists 

 and geologists, whose evidence as experts will undoubtedly 

 have great weight with the educated public, are at present 

 altogether in his favour. 



Hovj Neiu Species have Originated. 



Leaving this great case to be discussed and argued in 

 weighty volumes by specialists in science, I here propose 

 to deal briefly with that much smaller but still important 

 question, of the origin of the species of a genus or of a 

 family — that is, of groups of organisms differing, as the 

 wolf, dog, and fox differ, among animals, or as the numerous 

 species of oaks or of primulas differ, among plants ; and I 

 hope to be able to show that in these cases there is hardly 

 any room for doubt as to the mode in which the change 

 from species to species has been effected. 



We have to inquire, then, how it is that new species 

 have arisen, supposing the world to have been then very 

 much as it is now ; and what becomes of them after they 

 have arisen. In the first place we must remember that 

 new species can only be formed when and where there is 

 room for them. If a continent is well stocked with animals 

 and plants, there is a balance between the different species, 

 those best adapted to the varied existing conditions main- 

 taining themselves in the largest numbers, while others, 

 being only adapted to special conditions that occur in 

 limited areas, are far less numerous; the former are 

 common and widespread, the latter rare or local species. 

 If the entire group of organisms in any coimtry has existed 

 for a sufficient time to have been subjected to all the 



