96 THE BERMUDA ISLANDS. 



the other ; hence, the forms of the Eastern United States, except 

 in so far as they may be also members of the southern fauna, 

 are almost entirely absent from the Bermudas. 



6. Most of the temperate-American element of the Ber- 

 mudian fauna owes its establishment on the islands to acci- 

 dental causes storm-winds ; the tropical (Neotropical element) 

 is, on the other hand, the expression of slow but steady diffusion. 



7. Neotropical elements largely preponderate in the perma- 

 nent or resident fauna of the islands. 



8. An arm of the sea may be as insuperable a barrier to the 

 passage of marine animals as it would be to the animals of the 

 land ; caution is hence necessary in the discussion of conti- 

 nental and oceanic changes or stability as affecting animal 

 distribution. 



