250 THE WORLD OF LIFE 



area in South America in which these Tertiary marsupials have 

 been found, taken in connection with the enormous areas of 

 geologically unexplored land in Asia and Australia, should make us 

 very cautious in assuming such vast and physically improbable 

 changes of land and sea at such a comparatively recent epoch. 

 The theory of land-connection also introduces enormous difficulties 

 of various kinds which it is well briefly to consider. If we suppose 

 an absolute land-connection in order to allow the marsupial type to 

 have entered Australia from temperate South America, we have 

 to face the incredible fact, that of the whole varied mammalian 

 fauna of the latter country this one group only was transmitted. In 

 these same deposits there are found ancestral hoofed animals of 

 small size (Pyrotherium) ; numerous rodents allied to cavies and 

 porcupines ; a host of Edentata allied to sloths, ant-eaters, and 

 armadillos. These, taken altogether, are many times more 

 numerous than the marsupials ; they were more varied in structure 

 and mode of life; and it is almost incredible that not one 

 representative of these somewhat higher forms should have reached 

 the new country, or having reached it should have all died out, 

 while the inferior group alone survived. Then, again, we know that 

 birds and insects must have abounded in South America at the 

 same period, while the whole 7000 miles of connecting land must 

 have been well clothed with vegetation to support the varied life 

 that must have existed upon it during the period of immigration. 

 Yet no indication of a direct transference or interchange of these 

 numerous forms of life in any adequate amount is found in either 

 Australia or South Temperate America. We can hardly suppose 

 such an enormous extent of land to have been raised above the 

 ocean ; that it should have become sufficiently stocked with life to 

 serve as a bridge (7000 miles long !), and that a few very small 

 marsupials only should have crossed it ; that it then sank as 

 rapidly as it had been formed ; with the one result of stocking 

 Australia with marsupials, while its other forms of life plants, birds, 

 insects, molluscs show an unmistakable derivation from the 

 Asiatic continent and islands. A careful examination of a large 

 globe or South Polar map, with a consideration of the diagram of the 

 proportionate height of land and depth of ocean at p. 345 of my 

 Darwinism, together with the argument founded upon it, will, 

 I think, convince my readers that difficulties in geographical 

 distribution cannot be satisfactorily explained by such wildly 

 improbable hypotheses. If the facts are carefully examined, it will 

 be found, as I have shown for the supposed "Atlantis" and 

 " Lemuria," that such hypothetical changes of sea and land always 

 create more serious difficulties than those which they are supposed 

 to explain. People never seem to consider what such an explana- 

 tion really means. They never follow out in imagination, step by 



