lOO CinCU.MSTANCES FAVORABLE TO THE Ciiap. IV, 



have l.ccn produced llicre, and nowhere else in the world. 

 Hencn^ :m oceanic ishxnd at first sie^ht seems to have been 

 hig'hly favorable for the production of new species. But we 

 may thus deceive ourselves, for, to ascertain whether a small, 

 isolated area, or a large open area like a continent, has been 

 most favorable for the production of new organic forms, we 

 ought to make the comparison -within equal times ; and this 

 wc are incajiahlo of doing. 



Although isolation is of great importance in the production 

 of new species, on the Avhole I am inclined to believe that large- 

 ness of area is still more important, especially for the produc- 

 tion of species which shall prove capable of enduring for a long 

 period, and of spreading Avidcly. Throughout a great and open 

 area, not only Avill there be a better chance of favorable varia- 

 tions arising from the large number of individuals of the same 

 species there supported, but the conditions of life are much 

 more complex from the large number of already existing spe- 

 cies ; and if some of these many species become modified and 

 improved, others will have to be improved in a corresponding 

 degree, or they will be exterminated. Each new form, also, as 

 soon as it has been much improved, will be able to spread over 

 the open and continuous area, and will thus come into compe- 

 tition with many others. Moreover, great areas, though now 

 continuous, owing to former oscillations of level, will often 

 have existed in a broken condition, so that the good effects of 

 isolation will generally, to a certain extent, have concuiTed. 

 Finally, I conclude that, although small isolated areas probably 

 have beeii in some respects highly favorable for the production 

 of new species, yet that the course of modification will gener- 

 ally have been more rapid on large areas ; and, what is more 

 important, that the new forms j)roduced on large areas, which 

 already have been victorious over many competitors, will be 

 tliose that will s])rea(l most widely, will give rise to most new 

 varit^ties and species, and will thus play the most important 

 part in the changing history of the organic Avorld. 



We can, perhaps, on these Aiews, imderstand some facts 

 wliich will be again alluded to in our chapter on Geographical 

 Distribution ; for instance, that the ]iroductions of the smaller 

 continent of Australia are now yielding before those of the 

 larger Europa'o- Asiatic area. Thus, also, it is that continental 

 pniductions have everywhere become so largely naturalized on 

 islands. On a small island, the race for life will have been less 

 severe, and there will have been less modification and less ex- 



