ACCIDENTAL DISPERSAL 301 



Man has brought the brown and the black rats apparently. 

 Why should the agencies of accidental transport have been 

 so much more potent in the distant past than they are 

 now ? We might add also, is it possible that these same 

 agencies should be able to select the most ancient forms of 

 life as more suitable for transport than more modern pro- 

 ductions ? Of course, these ideas of mammals being carried 

 across a vast expanse of ocean and safely landed on a distant 

 shore are mere conjectures unsupported by any evidence. 



" Of land-birds," says Mr. Darwin, " I obtained twenty-six 

 kinds, all peculiar to the archipelago and found nowhere else, 

 with the exception of one lark -like finch (Dolichonyx oryzi- 

 vorus) from North America." Of waders and water-birds he 

 succeeded in capturing eleven kinds, only three of them being 

 new species. In 1875 the number of land-birds known to Mr. 

 Salvin had increased from twenty-five to thirty-six species. 

 Most of the genera to which they belong are of very wide 

 distribution ; seven, however, are confined to continental 

 America, leaving five peculiar to the islands. Mr. Salvin * 

 expresses no doubts as to the correctness of Darwin's inter- 

 pretation of the origin of the Galapagos islands. Hence he 

 concludes that the birds now found on the islands, being 

 related to American birds, must have emigrated from' America 

 and have become modified by the different climatic condi- 

 tions with which they were surrounded. A later review of the 

 Galapagos birds was undertaken by Mr. Bidgway f in 1897, 

 when the number of land-birds recorded from the islands was 

 nearly doubled. He notes the exact distribution of the various 

 species and varieties in detail, and shows how circumscribed 

 their range is. Of the five genera peculiar to the islands 

 only two, viz., Nesomimus and Nesopelia are of evidently 

 American relationship. The remaining three, he thinks, have 

 so obvious a leaning towards certain Hawaiian dicaeidine 

 forms, that the possibility of a former land connection with 

 the Sandwich islands, either continuous, or by means of inter- 

 mediate islands as " stepping stones," becomes a factor in 

 the problem of their origin. "It may be," he adds, "that 

 the resemblance of Cocornis, Cactornis and Camarhynchus 



* Salvin, 0., " Avifauna of Galapagos Archipelago." 



t Eidgway, E., " Birds of Galapagos Archipelago," p. 467. 



