1897.] The Origin of the Galapagos Islands. 671. 
much to do with his later conception of the origin of species. 
The fact on which he laid special stress was that the genera, to 
a very great extent, were the same as in all the islands, and 
the species different in each island. Dr. Baur’s much more 
extensive zoological and botanical collections and observations 
confirm and emphasize the correctness of the view of his illus- 
trious predecessor of fifty years ago. Darwin especially refers 
to the existence of different species or races of tortoises and 
mocking-thrushes [Nesomimus] in many of the islands; and 
Baur’s examination of the lizards of the genus Tropidurus, from 
twelve of the islands, reveals the same condition of things. The 
botanists bring forward Euplorbia viminea in illustration of this 
phenomenon. This species was described by Sir Joseph Hooker 
from a single specimen collected by Macrae in Albemarle 
Island, and the author remarks that. he “knew of no species 
with which to compare this highly curious one.” Dr. Baur 
collected it extensively in eight of the islands, and the speci- 
mens from almost every one of them [7] exhibit distinct racial 
characteristics. Acalaphe, a genus of the same natural order, 
presents somewhat more pronounced variation in the different 
islands, which some botanists regard as of specific value; other 
botanists, as of varietal value only. Whatever status we give 
these forms, the flora asa whole is a most instructive and con- 
vincing illustration of evolution. 
“A remarkable peculiarity of the Galapagos flora as an in- 
sular flora is the almost total absence of endemic genera, for 
the two or three genera of the Composite restricted to the 
islands are so closely allied to the American genera as hardly 
to count as distinct. Indeed, the whole flora is so thoroughly 
‘American that, apart from geological difficulties, it might be 
regarded as a differentiated remnant thereof, rather than de- 
rived therefrom, after the supposed elevation of the islands. 
Analogous conditions and phenomena are repeated in the deep 
valleys of the great mountain chains of northern India and 
western China, where, in neighboring valleys, the genera are 
to a great extent the same and the species different. 
“Looking at the composition of the Galapagos flora, espe- 
cially with an eye to the probabilities of the transport of the 
