432 ORIGIN OF SPECIES 



only all the individuals of the same species have migrated 

 from some one area, but that allied species, although now 

 inhabiting the most distant points, have proceeded from a 

 single area, — the birthplace of their early progenitors. I 

 have already given my reason for disbelieving in continental 

 extensions within the period of existing species, on so enor- 

 mous a scale that all the many islands of the several oceans 

 were thus stocked with their present terrestrial inhabitants. 

 This view removes many difficulties, but it does not accord 

 with all the facts in regard to the productions of islands. In 

 the following remarks I shall not confine myself to the mere 

 question of dispersal, but shall consider some other cases 

 bearing on the truth of the two theories of independent crea- 

 tion and of descent with modification. 



The species of all kinds which inhabit oceanic islands are 

 few in number compared with those on equal continental 

 areas: Alph. de Candolle admits this for plants, and Wollas- 

 ton for insects. New Zealand, for instance, with its lofty 

 mountains and diversified stations, extending over 780 miles 

 of latitude, together with the outlying islands of Auckland, 

 Campbell and Chatham, contain altogether only 960 kinds of 

 flowering plants ; if we compare this moderate number with 

 the species which swarm over equal areas in South-Western 

 Australia or at the Cape of Good Hope, we must admit that 

 some cause, independently of different physical conditions, 

 has given rise to so great a difference in number. Even the 

 uniform county of Cambridge has 847 plants, and the little 

 island of Anglesea 764, but a few ferns and a few intro- 

 duced plants are included in these numbers, and the compari- 

 son in some other respects is not quite fair. We have 

 evidence that the barren island of Ascension aboriginally 

 possessed less than half-a-dozen flowering plants; yet many 

 species have now become naturalised on it, as they have in 

 New Zealand and on every other oceanic island which can 

 be named. 



In St. Helena there is reason to believe that the natu- 

 ralised plants and animals have nearly or quite extermi- 

 nated many native productions. He who admits the doctrine 

 of the creation of each separate species, will have to admit 

 that a sufficient number of the best adapted plants and ani- 



