CHAP. XII.] 
BERMUDA. 
263 
occasionally bring seeds, either in the mud attached to their feet 
or in their stomachs. 1 As these causes are either constantly in 
action or recur 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 which 
determine the island -population. In both islands the land-birds 
are almost exclusively migrants ; and in both, the n on-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. Mose’ey. ( Journal 
of the Linnean Society , Vol. XIV., “ Botany,” p. 317.) 
