214 Hints on the Geographical Distribution of Animals. 



geographically separate since an era anterior to the introduction 

 of the existing species. But this conclusion does not depend on 

 the assumption that the species would have dispersed them- 

 selves over several islands if they had not always been 

 restrained by water ; but on the fact that such small zoological 

 provinces exist nowhere on continents.* 



80. The occurrence of a very few identical species on different 

 islands, or on islands and the mainland, does not prove the 

 union of such land since the existence of the species, because 

 such a distribution may have been caused by the accidents of 

 dispersion, or (§ 27) by independent creation. 



31. If the time, when any islands were once united, can be 

 proved geologically to have been more remote than the intro- 

 duction of existing species, any facts relating to the distribution 

 of the existing species cannot prove the union of such islands. 

 This is a truism, but it seems to have been sometimes for- 

 gotten. 



32. The occurrence of many species common to different 

 islands, in some parts of Polynesia, renders it probable that 

 such islands have constituted one island since the existence of 

 these species. 



38. The frequent occurrence of analogues and the prevalence 

 of generic or subgeneric types in some islands do not prove the 

 former union of these islands, but may indicate their greater 

 proximity at a former period (v. § 18). 



34. An apparent exception to § 18 is mentioned by Dr. Gould 

 (Introd. Eep. Moll. Expl. Exped.). The Samoa and Friendly 

 Islands are moie intimately related zoologically to the Society 

 Islands, ti>au to the Feejee Islands, although the latter are much 

 nearer. Hence we may infer the greater magnitude and prox- 

 imity to each other at some former period of the Samoa, 

 Friendly, and Society Islands. 



The above hints have been hastiW written down. Thc}^ may 



* The very liniitod distribution of certain tribes of animals is not an exception 

 to this statement, whicli has reference to the general fauna of a conntrv. 



