254 PROCEEDINGS OF THE AMERICAN ACADEMY. 
any question. It is strongly supported by the following facts: (1) All 
parts of the islands now visible are obviously of volcanic origin. (2) The 
islands are separated from the mainland by a very considerable depth of 
ocean (more than 1500 fathoms). (8) The western coast of South 
America shows no signs of subsidence, but rather of marked elevation in 
recent geologic time. 
In accordance with this theory of emergence, the flora of the Galapagos 
Islands is assumed to have been brought to them by the ordinary agents 
of plant-distribution, namely, the wind, oceanic currents, and migratory 
birds. Moreover, it is not difficult to see the probable efficiency of these 
means of seed-transportation in the present case. The islands lie in the 
course of pretty constant trade winds, doubtless capable of bearing spores 
and small seeds to a great distance, as winds have been known to carry 
fine particles of sand and pumice for hundreds of miles. The great ocean 
current which sweeps along the west coast of Mexico, and the Humboldt 
Current, which runs northward along the coast of Chili and Peru, both 
turn westward just in the equatorial belt where the islands lie. That the 
current between Central America and the Galapagos has considerable 
seed-carrying power, seems more than probable from the interesting 
observations of Mr. Alexander Agassiz (1), 59, 69, who while dredging 
that part of the Pacific found the bottom “strewn thickly with vegetable 
matter, which came up in great masses in almost every haul of the 
trawl.” He states also that: “The velocity of the currents in the 
Panama district is very great, sometimes as much as seventy-five miles a 
day, so that seeds, fruits, masses of vegetation harboring small reptiles, or 
even large ones, as well as other terrestrial animals, need not be afloat 
long before they might safely be landed on the shores of the Galapagos.” 
It may here be noted that Hooker (4), 256, has shown that a large pro- 
portion of the plants of the Galapagos Islands are provided with special 
means of seed-dispersal, — a fact of interest in this connection. 
But, however probable the pelagic origin of the islands seems from the 
data above presented, Dr. Baur has pointed out what has appeared to be 
a fatal defect in this theory. For, although it may be quite possible to 
explain the presence of plants and some animals upon islands of emer- 
gence, it is much more difficult if not impossible to explain upon the same 
theory the extraordinary biological relations between these islands them- 
selves. An examination of the flora shows that many plants on the 
different islands are nearly related to each other, without being exactly 
the same. For instance, each of several islands has a peculiar species 
_ of Sealesia, a genus confined to the archipelago. There are also on 
