Chap. XI [. INHABITANTS OF OCEANIC ISLANDS. 355 



and having subseqiienlly become extinct in intermediate re- 

 gions. But the wide distribution of fresli-wuter pkxnts and of 

 the lower animals, whether retaining the same identical form 

 or in some degree modifieJ, I believe mainly depends on the 

 wide disjiersal of their seeds and eggs by animals, more es- 

 pecially by fresh-water birds, which have great poAvers of 

 flight, and naturally travel from one piece of water to another. 



On the InJuihltayds of Oceanic Islcmds. 



We now come to the last of the three classes of facts, 

 which I have selected as presenting the greatest amount of 

 dilliculty, if we accept the view that not only all the individ- 

 uals of the same species, wherever found, have migrated from 

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

 the most distant points, have proceeded from a single area — 

 tlie birthplace of their early prog(Miitor. I have already stated 

 that I cannot honestly admit For])es's view en continental ex- 

 tensions, which, if legitimately followed out, would lead to the 

 belief that all existing islands have been continuously or 

 almost continuously joined to some continent within the recent 

 period. This view Avould remove many dilliculties, but it 

 would not explain all the facts in regard to insular produc- 

 tions. In the following remarks I shall not confine myself to 

 the mere question of dispersal ; but shall consider some other 

 facts, which bear on the truth of the two theories of indepen- 

 dent creation and of descent with modification. 



The species of all kinds which inhabit oceanic islands are 

 few in number compared Avith those on equal continental 

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

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

 moimlains and diversified stations, extending over 780 miles 

 of latitufle, together with the outlying islands of Auckland, 

 Campbell, and Chatham, contain altogether only DCO lands 

 of flowering plants; if we compare this moderate number with 

 the species which swann over equal areas in Southwestern 

 Australia or at the Cape of Good Ilojie, we nnist admit that 

 somclliing, quite indcpenilently of a difVerence in tlie ])hvsical 

 conditions, has caused so great a difVerence in number. Even 

 the uniform county of Cambridge has 847 plants, and the little 

 island of Anglesea 704, but a few ferns and a few introduced 

 plants are included in these nundiers, and the comparison in 

 some other respects is not quite fair, "\\'e have evidence that 



