336 ON THE ORIGIN OF SPECIES 



geological sense, it seems to me probable that it was, dur- 

 ing a part at least of the period, actually simultaneous 

 throughout the world. Without some distinct evidence 

 to the contrary, we may at least admit as probable 

 that the glacial action was simultaneous on the eastern 

 and western sides of North America, in the Cordillera 

 under the equator and under the warmer temperate 

 zones, and on both sides of the southern extremity 

 of the continent. If this be admitted, it is difficult 

 to avoid believing that the temperature of the whole 

 world was at this period simultaneously cooler. But 

 it would suffice for my purpose, if the temperature 

 was at the same time lower along certain broad belts 

 of longitude. 



On this view of the whole world, or at least of broad 

 longitudinal belts, having been simultaneously colder 

 from pole to pole, much light can be thrown on the 

 present distribution of identical and allied species. 

 In America, Dr. Hooker has shown that between forty 

 and fifty of the flowering plants of Tierra del Fuego, 

 forming no inconsiderable part of its scanty flora, are 

 common to Europe, enormously remote as these two 

 points are ; and there are many closely allied species. 

 On the lofty mountains of equatorial America a host of 

 peculiar species belonging to European genera occur. 

 On the highest mountains of Brazil, some few European 

 genera were found by Gardner, which do not exist in 

 the wide intervening hot countries. So on the Silla of 

 Caraccas the illustrious Humboldt long ago found 

 species belonging to genera characteristic of the Cordil- 

 lera. On the mountains of Abyssinia, several European 

 forms and some few representatives of the peculiar flora 

 of the Cape of Good Hope occur. At the Cape of Good 

 Hope a very few European species, believed not to have 

 been introduced by man, and on the mountains, some 

 few representative European forms are found, which 

 have not been discovered in the intertropical parts 

 of Africa. On the Himalaya, and on the isolated 

 mountain -ranges of the peninsula of India, on the 

 heights of Ceylon, and on the volcanic cones of Java, 



