358 ORGANIC EVOLUTION CONSIDERED 



In this he considers the variations in color of closely- 

 related species of beetles, snakes, and lizards. If all 

 that he claims here be true, yet it would be of little 

 importance in establishing the truth of the theory of 

 evolution, for it is well known that color has little, if 

 any thing, to do with structure, and that it is with 

 changes of structure that evolution is concerned. 



He next considers variations in North American 

 birds and mammals in relation to locality. He shows 

 that certain species of birds and mammals vary in the 

 size of the individuals composing them, and that the 

 latter vary somewhat in the relative size of certain 

 organs. Size alone of individuals does not determine 

 species. 



Then follows a brief statement of a few variations 

 in structural characters, in which it is shown that 

 among dogs the number of teeth varies somewhat, 

 and, also, that their structure varies slightly. The 

 same things occur among the teeth of different men. 



It is not certain that the different kinds of dogs 

 have all been derived from one species, and this may 

 help to account for fewer teeth in some. 



He endeavors to show, by comparing their skele- 

 tons, that the various species of Batrachia (= frogs, 

 toads, etc.), have had a common origin. The origin 

 of species cannot be determined by simply comparing 

 skeletons. Such comparisons are, of course, neces- 

 sary for the theory of evolution, but much more is 

 required than this in order to account for new species. 



He attributes to isolation a large share in the for- 

 mation of species. He says: "That existing types 

 of all grades are the result of the isolation of varia- 

 tions of species, is shown by the frequent examples of 

 incomplete isolation, which follows inconstancy of the 

 definitive characters." * 



* Page 62. 



