662 The American Naturalist. [August, 
islands will be affected gradually in the same way ; there will 
be immigrants from other localities besides the original in- 
habitants. * 
“Continental islands, therefore, may be composed of two floral and 
faunal elements: first, an original (endogenous) one; and second, 
a secondary (exogenous) one. Oceanic islands, however, will only 
contain a secondary (or exogenous) floral and faunal element, they 
never will show harmonic distribution.” 
By the study of the Galápagos Islands I reached the con- 
clusion that the distribution of the animals was harmonic, and 
that the theory of the oceanic origin was therefore not correct. 
This opinion I have sustained in the following papers: 1. 
Das Variiren der Eidechsen-Gattung Tropidurus auf den Galá- 
pagos Inseln., Biol. Centralbl, Vol. X, 1890, p. 475-483. 
2. Account of my Trip to the Galapagos Islands, dated Chat- 
ham Island, August 28, 1891, Amer. Nar., Vol. XXV, 1891, p- 
902-907. 3. Ein Besuch der Galápagos Inseln., Biol. Centralbl., 
Vol. XII, 1892, p. 221-250, also H. de Varigny. Voyage scien- 
tifique aux Isles Galápagos, Revue Scientif., Vol. 50, No. 13, 
24 Sept., 1892, p. 391-400. 4. Das Variiren der Eidechsen- 
Gattung Tropidurus auf den Galápagos Inseln. Festschrift zam 
siebenzigsten Geburtstage Rudolf Leuckart’s, Leipzig, 1892, 
p. 259-277, 4° (with variation curves). 5. The Differentiation 
of Species on the Galápagos Islands and the Origin of the 
Group, Biol. Lect. Marine Biol. Laborat. Wood’s Holl., 1894, 
Boston, 1895, p. 67-78. 
In this last paper I gave a table showing the distribution of 
seven genera on the Galápagos Islands; I also gave a table of 
the distribution of seven genera of birds on the West Indies. 
Since the West Indies show harmonic distribution, and since 
it is proved that they were formed by the splitting up of a con- 
tinuous land area, the same must be true for the Galápagos. 
This paper has been reviewed by Professor F. Ratzel in 
Leipsic, Professor S. Günther in Munich, and Professor O. 
Böttger in Frankfort. They all agree with my view. Ratzel 
says: “ Baur concludes from the‘ harmonic distribution ’ of the 
variations that the Galápagos, like the Antilles, originated by 
sinking of the sea bottom, and were certainly not formed by 
