PENDULATION THEORY 
435 
pense with land connections, and he rejects the theories of 
accidental dispersal as quite inapplicable to the solution of the 
antarctic biological problems. For my own part, I think that 
changes of land and water, combined with warm currents in 
the Polar regions, would likewise explain the same phenomena 
in a satisfactory manner, and I prefer to adopt the latter view 
until we possess more definite information as to evidence on 
which the pendulation theory is founded. 
I have endeavoured in this work to show how the gradual 
evolution of our continents and the former changes of land 
and water can be demonstrated by a study of the geographical 
distribution of living animals and plants. Whenever possible 
I have taken advantage of our palaeontological and geological 
knowledge in furtherance of this object, and I venture to 
think that I have succeeded in unravelling some intricate 
problems of the palaeogeography of America. Indirectly I 
have thus been able to indicate the manner in which North 
and South America became populated, and the extent to 
which these continents took part in supplying animals and 
plants to other regions of the world. 
f f 2 
