360 THE CONCEPT OF EVOLUTION 



young and young feeding mothers, in the way the tailor- 

 ants use their children as needle and thread! 



§ 4. Definition of the Concept of Organic Evolution, 



By a method of contrast, then, we are seeking to render 

 more precise the concept of organic evolution. It is distin- 

 guishable from the genesis of the solar system or of a range of 

 mountains, and from the history of political institutions or 

 social usages. Moreover, we speak of the development of 

 the chick, but of the evolution of birds. What more can 

 be said ? Organic evolution is a continuous natural process 

 of racial change in a definite direction whereby distinctively 

 new individualities arise, take root, and flourish, sometimes 

 alongside of, and sometimes, sooner or later, in place of the 

 originative stock. The domestic breeds of pigeons and fowls 

 are apparently the results of evolutionary change whose 

 origins are still with us in the Rock Dove and the Jungle 

 Fowl. In the Crab-Apple by the wayside, whose promise 

 is more obviously suggested by its flowers than by its fruit, 

 there is the sturdy plebeian ancestor of all the delicate aristo- 

 crats of the orchard ; into the unpromising wild kale by the 

 sea-shore we have to read back all our cabbages, cauliflowers, 

 and curly greens. In these and in many other cases the 

 original stock still persists. 



It is otherwise, however, when we inquire into the origin 

 of creatures like the domestic horse or dog; the only certainty 

 is our ignorance. And this is even more emphatic when 

 we try to discover the pedigree of any of the great classes 

 of animals: Whence came mammals or birds? What was 

 the origin of molluscs or of insects? In many cases the 

 ancestral stocks are unknown ; in other cases where they 

 have been detected by some probability they are separated by 



