I42 THE AMERICAN NATURALIST. 
tendency to restrict the boundaries of this continent to reason- 
able dimensions, thus approaching Hedley's ideas. 
Other writers have only added new facts to the material 
already at hand that favors the assumption of a former conti- 
nental connection of the southern regions, and they have all 
accepted the general idea of Hooker and Ruetimeyer, without 
making any material change in it; therefore I do not consider 
it necessary to mention them here. 
We may sum up all theories advanced, and put them into a 
table in the following way : 
I. Theories assuming a land connection between the respective parts. 
This general idea was first expressed by Hooker (1847). It has 
been accepted by all subsequent writers except Wallace. 
1. The land bridge is placed across the present Antarctic continent, 
first by Ruetimeyer (1867) and by Hutton (1873). It was 
accepted by Von Ihering, Forbes, Hedley, Osborn. 
(a) Forbes constructs his immense Antarctica (1893). 
(^) Hedley restricts it to reasonable limits (1895). 
(c) Osborn takes an intermediate standpoint (1900). 
2. Gill constructs his Eogzea, a continent uniting Africa, South America, 
and Australia, but leaving out the Antarctica (1875). 
3. Hutton connects Australia and South America by his mid-Pacific 
continent, but denies the existence of an Antarctic connection 
(1884). 
II. Theory of Wallace (1876) rejecting any land connections whatever 
between the respective parts. 
I do not want here to go into any further detail, since my 
only purpose is to give an account of the existing theories with 
proper references, and to classify them according to their 
contents. But I may state here that in the forthcoming 
report on the Patagonian fossils mentioned above, I shall accept 
Hooker's general idea, as well as Ruetimeyer's Antarctica 
theory, with the restrictions put upon it by Hedley, and thus 
we may call it 7e Hooker-Ruetimeyer-Hedley theory. 
PRINCETON UNIVERSITY. 
