Alfred Russel Wallace 



able station would prevent an invader, especially from a 

 quite foreign province, from having a chance of making 

 good his settlement in a new country. But Darwin and 

 Hooker contend that continental species which have been 

 improved by a keen and wide competition are most 

 frequently victorious over an insular or more limited flora 

 and fauna. Looking, therefore, upon Bali as an outpost 

 of the great Old World fauna, it ought to beat Lombok, 

 which only represents a less rich and extensive fauna, 

 namely the Australian. 



You may perhaps answer that Lombok is an outpost 

 of an army that may once have been as multitudinous as 

 that of the old continent, but the larger part of the host 

 have been swamped in the Pacific. But they say that 

 European forms of animals and plants run wild in Aus- 

 tralia and New Zealand, whereas few of the latter can do 

 the same in Europe. In my map there is a small island 

 called Nousabali; this ought to make the means of migra- 

 tion of seeds and animals less difficult. I cannot find that 

 you say anywhere what is the depth of the sea between the 

 Straits of Lombok, but you mention that it exceeds 100 

 fathoms. I am quite willing to infer that there is a con- 

 nection between these soundings and the line of demarca- 

 tion between the two zoological provinces, but must we 

 suppose land communication for all birds of short flight ? 

 Must we unite South America with the Galapagos Islands ? 

 Can you refer me to any papers by yourself which might 

 enlighten me and perhaps answer some of these queries ? 

 I should have thought that the intercourse even of savage 

 tribes for tens of thousands of years between neighbouring 

 islands would have helped to convey in canoes many animals 

 and plants from one province to another so as to help to 

 confound them. Your hypothesis of the gradual advance 

 of two widely separated continents towards each other 



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