E i'OL UTION, 29 



kind ; why many organisms are absent from islands ; 

 and how barriers of mountains or deep straits affect 

 the character of life in the lands on either side. 



It was the observation of the absence from the 

 Gallapagos Islands of many animals that can neither 

 fly nor swim that led Darwin, in his voyage in the 

 Beagle, to the reflection that produced his theo- 

 ries. Why the Creator should not have made frogs 

 in islands is a question that the special-creation theory 

 does not answer. Frogs cannot swim far, and have 

 stayed at home on the continents. The life upon 

 islands corresponds to that of the mainlands nearest 

 to them, and consists of such kinds as can be trans- 

 ported. 



It was wondered why kangaroos and some other 

 types of life were confined to Australia. Wallace 

 has pointed out the deep channel which severed 

 Australia from the nearest land, and prevented the 

 migration of animals. Australia was formerly joined 

 to the continent of Asia, and possessed similar forms 

 of life ; but becoming separated, she has preserved 

 the types that have perished elsewhere by the com- 

 petition of other animals, that the conditions of her 

 climate did not tend to develop, and were prevented 

 by the Straits of Lombok from coming to her lands. 



The regions that have been most completely sepa- 

 rated from others have the most distinct types of 

 life, and where facility for the migration of animals 

 and for the conveyance of seeds has been greatest, 

 there we find the greatest variety of forms. 



