maps (Fig. 1) in order immediately to read from them the explanation. Even these purely biological facts show the distinct advantages which the displacement theory possesses over that of the submerged bridges. The distance from the nearest points of South America and Australia, namely, Tierra del Fuego and Tasmania, amounts to-day to 80°, measured along a great circle, that is, quite as much as that between Germany and Japan. Central Argentina lies just as far from Central Australia as from Alaska, or as South Africa from the North Pole. Does one really believe that a mere land connection is sufficient to secure the exchange of forms? And how strange it is that Australia had no interchange of forms with the immediately adjoining Sunda Islands to which it is like a foreign body from another world! No one can deny that our assumption, which reduces the distance of Australia from South America to a fraction, and on the other hand separates it from the Sunda Islands by a broad ocean basin, provides a key for the explanation of the Australian animal kingdom.
