1897.] The Origin of the Galapagos Islands. 667 
either united, or at least that the channels which separate them 
were less formidable barriers to seed transportation than at 
present, so that general distribution of species could have been 
effected ; and that subsequently, as the islands separated, or as 
the channels through some change of currents, or other cause, 
became less easily passed, an era of much greater isolation of 
the floras of the different islands came about. The divergence 
of character of the vegetation would then begin at once, and 
the otherwise unaccountable existence of a single and peculiar 
form upon each island would be readily intelligible.” 
While not prepared to make any positive assertion regard- 
ing the probable origin of the islands, the authors fail to see 
in the hitherto generally accepted theory of elevation any 
satisfactory explanation for the harmonic yet divergent floras 
of the different members of the group. Upon Dr. Baur’s as- 
sumption of a former union between the islands and subse- 
quent separation by subsidence, not only is explanation 
possible, but the existing flora of the archipelago is just that 
which would most naturally result from such an origin. A 
former union of the islands would account at once for the 
occurrence of identicai ancestral species upon the different 
members of the group, and the subsequent separation give the 
needed isolation for varietal and racial divergence, while the 
latter could not have come about if a continental interchange 
of seeds were taking place from island to island. 
Regarding a former land-connection with the continent, 
which would certainly offer much greater geological difficul- 
ties, the botanical evidence is still too vague to merit regard. 
The affinities of the vegetation of the upper, moister portions 
of the islands are doubtless, as has been assumed, with the 
floras of Columbia, Central America, Southern Mexico, and the 
West Indies, while much of the desert flora of the lower regions 
has doubtless been derived from the arid regions of Chili and 
Peru. But, so far as botanical data are concerned, this could 
have come about either by migration by land or by transporta- 
tion by oceanic currents, and, as the latter still exist, it seems 
unnecessary to assume the former. However, on this point, 
the evidence from the vegetation appears to be still wholly 
indecisive, 
