40 THE VICTORIAN NATURALIST. 



intervening tracts, and it is one of the tasks of the modern 

 zoogeographer to trace out not only the route by which they 

 spread, but the date of their march. 



Some groups of animals are ancient, others are young. The 

 Pigs are old, but full of vigour, while the Tapirs are also old, but 

 dying out, while, on the other hand, the perching birds, or 

 Passerines, are still in their vigorous youth. The connecting links 

 are still so abundant that we see relationships for every bird in 

 half a dozen different directions, and this it is that inai<es the 

 successful classification of the group such an insoluble puzzle. 



The grouping of the lands of to-day is but a passing phase, and 

 geologists talk freely of land-bridges across what is now deep sea, 

 and of deep and wide seas extending over what is now dry land. 

 Mammal and bird, snail and earthworm, frog and fresh-water 

 crayfish, all find the sea, even a narrow strait, an impassable 

 barrier ; yet they are found in all lands, for 



" He hath made the deep as dry, 

 He hath smote for us a pathway to the ends of all the earth." 



We ought, then, by a study of the present distribution of animals, 

 and without the aid of geology to be able to plot the outlines of 

 many of the ancient continents with a considerable amount of 

 accuracy. Merely by studying the animals and plants of 

 Tasmania, we can assert with confidence the presence of a former 

 land-bridge, which recently, as geologists regard itj allowed a free 

 intermingling of all forms of life. Comparing again our fauna 

 with that of Southern Asia, we can assert, though with less 

 certainty, that there was a connection, but that it broke down 

 before the present Australian animals could spread into Asia, or 

 Asiatic into Australia. 



Seeing, then, that these land connections formerly existed in 

 various places, we may consider the relationships of our fauna to 

 that of the rest of the world. One of the earliest facts that struck 

 botanists when they began to investigate Australia v/as that the 

 floras of Australia, South Africa, and South America are but 

 divided parts of one whole. This points to a former land 

 connection between the parts and isolation from the rest of the 

 world. The animals tell the same tale, though perhaps not so 

 plainly. Marsupials are now found only in America and 

 Australia, and the American opossums are so closely allied to the 

 family containing our native cats that their separation as a 

 distinct family is but barely justifiable. Extinct marsupials have 

 been found in Patagonia, which emphasize the relationship to 

 our fauna in a marked degree. Then an extinct horned lizard 

 has left its remains in Queensland, Norfolk Island, and Patagonia. 

 The group of Cystignathid Frogs, which comprises our Sand Frog 

 (Limnod'i/nastes), the Burrowing Frog of Central Australia, and 

 others, is elsewhere found only in South America. 



