CHAP. XII.] 



BERMUDA. 



263 



occasionally bring seeds, either in the mud attached to their feet 

 or in their stomachs.^ As these causes are either constantly in 

 action or resur annually, it is not surprising that almost all the 

 species should be unchanged owing to the frequent intercrossing 

 of freshly-arrived specimens. If a competent botanist were 

 thoroughly to explore Bermuda, eliminate the species introduced 

 by human agency, and investigate the source from whence the 

 others were derived and the mode by which they had reached 

 so remote an island, we should obtain important information as 

 to the dispersal of plants, which might afford us a clue to 

 the solution of many difficult problems in their geographical 

 distribution. 



Concluding Remarks. — -The two groups of islands we have now 

 been considering furnish us with some most instructive facts as 

 to the power of many groups of organisms to pass over from 

 700 to 900 miles of open sea. There is no doubt whatever that 

 all the indigenous species have thus reached these islands, and 

 in many cases the process may be seen going on from year to 

 year. We find that, as regards birds, migratory habits and the 

 liability to be caught by violent storms are the conditions v>^hich 

 determine the island -population. In both islands the land-birds 

 are almost exclusively migrants ; and in both, the non-migratory 

 groups — wrens, tits, creepers, and nuthatches — are absent ; while 

 the number of annual visitors is greater in proportion as the 

 migratory habits and prevalence of storms afford more efficient 

 means for their introduction. 



We find also, that these great distances do not prevent the 

 immigration of some insects of most of the orders, and espe- 

 cially of a considerable number and variety of beetles ; while 

 even land-shells are fairly represented in both islands, the large 

 proportion of peculiar species clearly indicating that, as we 

 might expect, individuals of this group of organisms arrive 

 only at long and irregular intervals. 



Plants are represented by a considerable variety of orders and 

 genera, most of which show some special adaptation for dispersal 

 by wind or water, or through the medium of birds ; and there is 



1 " Notes on the Vegetation of Bermuda," by H. N. Moseley. {Journal 

 of the Linnean Society^ Vol. XIV., Botany," p. 317.) 



