356 ON THE ORIGIN OF SPECIES 



lea and the degree of affinity of the mammalian inhabit- 

 ants of islands with those of a neighbouring continent, 

 — an inexplicable relation on the view of independent 

 acts of creation. 



All the foregoing remarks on the inhabitants of 

 oceanic islands, — namely, the scarcity of kinds — the 

 richness in endemic forms in particular classes or 

 sections of classes, — the absence of whole groups, as of 

 batrachians, and of terrestrial mammals notwithstand- 

 ing the presence of aerial bats, — the singular propor- 

 tions of certain orders of plants, — herbaceous forms 

 having been developed into trees, etc., — seem to me 

 to accord better with the view of occasional means 

 of transport having been largely efficient in the long 

 course of time, than with the view of all our oceanic 

 islands having been formerly connected by continuous 

 land with the nearest continent ; for on this latter 

 view the migration would probably have been more 

 complete ; and if modification be admitted, all the forms 

 of life would have been more equally modified, in 

 accordance with the paramount importance of the rela- 

 tion of organism to organism. 



I do not deny that there are many and grave diffi- 

 culties in understanding how several of the inhabitants 

 of the more remote islands, whether still retaining the 

 same specific form or modified since their arrival, could 

 have reached their present homes. But the probability 

 of many islands having existed as halting-places, of 

 which not a wreck now remains, must not be over- 

 looked. I will here give a single instance of one of 

 the cases of difficulty. Almost all oceanic islands, 

 even the most isolated and smallest, are inhabited by 

 land-shells, generally by endemic species, but some- 

 times by species found elsewhere. Dr. Aug. A. Gould 

 has given several interesting cases in regard to the 

 land-shells of the islands of the Pacific. Now it is 

 notorious that land-shells are very easily killed by salt ; 

 their eggs, at least such as I have tried, sink in sea- 

 water and are killed by it. Yet there must be, on 

 my view, some unknown, but highly efficient means 



