420 
ISLAND LIFE. 
[part. II. 
those which have been more or less secured by their isolated 
position from the incursions of the more highly-developed 
forms of later times. This explains why it is that the nearest 
allies of the Madagascar fauna and flora are now so often to be 
found in South America or Australia — countries in which low 
forms of mammalia and birds still largely prevail it being on 
account of the long-continued isolation of all these countries 
that similar forms (descendants of ancient types) are preserved 
in them. Had the numerous suggested continental extensions 
connecting these remote continents at various geological periods 
been realities, the result would have been that all these interest- 
ing archaic forms, all these helpless insular types, would long 
ago have been exterminated, and one comparatively monotonous 
fauna have reigned over the whole earth. So far from explain- 
ing the anomalous facts, the alleged continental extensions, had 
they existed, would have left no such facts to be explained. 
