420 
ORIGIN OF LIFE IN AMERICA 
arisen partly by accidental dispersal and partly by migration 
through the existing continents, when they were united hy 
short temporary land bridges in the far north. 
Sir Joseph Hooker seems to have been the first to formulate 
the theory of a former land connection of southern lands from 
the occurrence of identical species of plants in widely 
separated areas. The first to mention an antarctic continent 
in this connection was Professor Ruetimeyer. This was 
twenty years later, in 1867. Six years elapsed after that until 
Professor F. W. Hutton again brought forward the theory, 
expressing his belief in the former existence of an antarctic 
land-mass and its union with the southern extremities of the 
present continents. A few years later Dr. Gill declared him¬ 
self in favour of a large continental mass embracing Africa, 
South America and Australia, his views being based on the 
geographical distribution of fishes. The fact that Dr. Wallace 
repudiated the opinions expressed by his predecessors need 
not be taken too seriously. Since his great work on the geo¬ 
graphical distribution of animals was issued, facts have been 
brought to light which are so overwhelmingly in favour of 
some kind of continuous land connection between South 
America and the Australian region that he could not at the 
present day assert, as he did then, that the affinities alluded to 
are mostly due to accidental dispersal across the ocean, aided 
by the presence of an antarctic land-mass unattached to other 
continents. Professor Hutton subsequently abandoned his 
theory of a land-bridge between the two regions by way of an 
antarctic continent in favour of a land connection right across 
the South Pacific towards the end of the Mesozoic Era.* 
In the year 1891, an important contribution to the subject 
was published by Dr. von Ihering.f He points out that the 
species of fresh-water Unio from New Zealand and adjoining 
countries have their nearest allies exclusively in Chile and 
southern Brazil, and that the fresh-water crayfishes (Para- 
stacidae) show the same character. The conclusions he de¬ 
rives from these and other facts are that the southern portions 
* Ortmann, A. E., “ Origin of Antarctic Faunas and Floras,” pp. 139— 
140. 
t Ihering, H. von, “ Relations between New Zealand and South 
America,” p. 442. 
