342 THE ORIGIN OF SPECIES 



and by subsequent intercrossing; and so it is known to 

 be under domestication, unless abrupt variations of this 

 kind are specially preserved and separated by the care of 

 man. Hence in order that a new species should suddenly 

 appear in the manner supposed by Mr. Mivart, it is al- 

 most necessary to believe, in opposition to all analogy, 

 that several wonderfully changed individuals appeared 

 simultaneously within the same district. This difficulty, 

 as in the case of unconscious selection by man, is avoided 

 on the theory of gradual evolution, through the preserva- 

 tion of a large number of individuals, which varied more 

 or less in any favorable direction, and of the destruction 

 of a large number which varied in an opposite manner. 



That many species have been evolved in an extremely 

 gradual manner there can hardly be a doubt. The spe- 

 cies and even the genera of many large natural families 

 are so closely allied together that it is difficult to distin- 

 guish not a few of them. On every continent in pro- 

 ceeding from north to south, from lowland to upland, 

 etc., we meet with a host of closely related or repre- 

 sentative species; as we likewise do on certain distinct 

 continents, which we have reason to believe were for- 

 merly connected. But in making these and the follow- 

 ing remarks, I am compelled to allude to subjects here- 

 after to be discussed. Look at the many outlying islands 

 round a continent, and see how many of their inhabitants 

 can be raised only to the rank of doubtful species. So 

 it is if we look to past times, and compare the species 

 which have just passed away with those still living 

 within the same areas; or if we compare the fossil spe- 

 cies imbedded in the sub-stages of the same geological 

 formation. It is indeed manifest that multitudes of spe- 



