1897.] The Origin of the Galapagos Islands. 673 
W. H. Dall,’ who has written the most extensive work on 
the landshells of the Galapagos Islands, also adopts the acci- 
dental introduction of the fauna. He says, p. 403: “ Omitting 
the Auriculide and Siphonariidx, we have, as supposed, pecu- 
liar forms in each group of islands: twenty-one characteristic 
of the southeastern, fourteen from the central, and one from the 
northeastern group of islands, which agree well with the hypo- 
thesis that the species originated with forms brought by winds 
and currents which impinge first on the southeastern group. 
On the other hand, itis certain that the southeastern islands 
are much better known than either of the other groups, and 
that the area and fertility of the central group are such 
that there is every reason to suppose many more forms remain 
to be discovered there, perhaps, including some of those so far 
known only from the southeastern islands. Prudence strongly 
urges, that we know too little of the mollusk fauna yet to in- 
telligibly discuss its inter-island distribution.” 
If the seeds of the different forms of Euphorbia viminea Hook. 
fil. are not blown or floated from one island to the other, as 
we have seen above, I cannot imagine that the landshells have 
been transported from island to island, or even from the Ameri- 
can continent. Why ought these animals form an exception 
from the other ones? ; 
Dr. Th. Wolf™ does not agree at all with the subsidence 
theory. He says: “ Every geologist will stand up against Dr. 
Baur’s hypothesis, until he shall have proved that it is abso- 
lutely indispensable for the explanation of the organic creation 
(organische Schdpfung) of the islands. The answering of the 
question: How have the present species of animals and plants 
been developed from the immigrated (or, according to Baur, 
the remaining) South American” species? is very difficult. 
Here opens, of course, an enormous field for speculation, and, 
as long as the opinions on the fundamental causes of the origin 
3 Dall, William Heally. Insular Landshell Faunas, Especially as Illustrated 
by the Data Obtained by Dr. G. Baur in the Galápagos Islands. Introductory. 
Proc. Acad. Nat. Sci.. Philadelphia, August, 1896, p. 395-459, Pl. XV-XVII. 
“Wolf, Dr. Th. Die Galdpagos-Inseln. Verhandl. Ges. Erdkunde. Berlin, 
Bd. XXII, 1895, No. 4u. 5. Berlin, 1895, p. 246-265, Taf. 3. 
13 I never said that they came from South America. 
