ANTARCTIC EXPLORATION. 297 



have reached New Zealand. New Zealand and South America have 

 three flowering plants in common, also two fresh- water fishes, five sea- 

 weeds, three marine crustaceans, one marine moUusk, and one marine 

 fish. Similarly New Zealand and Africa have certain common forms, 

 and the floras and faunas of the Kerguelen, the Crozets, and the Marion 

 Islands are almost identical, although in each case the Islands are very 

 small, and very isolated from each other and from the rest of the world. 

 Tristan d'Acunha has fifty-eight species of marine Mollusca, of which 

 number thirteen are also found in South America, six or seven in New 

 Zealand, and four in South Africa (Button's Origin of Neio Zealand 

 Flora and Fauna). Temperate South America has seventy-four genera 

 of plants in common with New Zealand, and eleven of its species are 

 identical (Wallace's Island Life). Penguins of the genus Eudyptes 

 are common to South America and Australia (Wallace, Bist. of 

 Animals, 1399). Three groups of fresh-water fishes are entirely con- 

 fined to these two regions. Aphritis, a fresh-water genus, has one 

 species in Tasmania and two in Patagonia. Another small group of 

 fishes known as the Haplochitonidie inhabit Tierra del Fuego, the 

 Falklands, and South Australia, and are not found elsewhere, while 

 the genus Galaxias is confined to South Temperate America, New Zea- 

 land, and Australia. Yet the lands which have these plants and 

 animals in common are so widely separated from each other that they 

 could not now possibly interchange their inhabitants. Certainly 

 towards the equator they approach each other rather more, but even 

 this fact fails to account for the present distribution, for, as Wallace 

 has pointed out, "the heat-loving Reptilia aflbrd hardly any indica- 

 tions of close affinity between the two regions" of South America and 

 Australia, "whilst the cold-enduring Amphibia and fresh-water fishes 

 offer them in abundance" (Wallace, Bist. of Animals, 1400). Thus 

 we see that to the north interchange is prohibited by tropical heat, 

 while it is barred to the south by a nearly shoreless circumpolar sea. 

 Yet there must have been some means of intercommunication in the 

 past, and it appears certain that it took the shape of a common father- 

 land for the various common forms from which they spread to the 

 northern hemisphere. As this father-land must have been accessible 

 from all these scattered southern lands, its size and its disposition must 

 have been such as would serve the emigrants either as a bridge or as 

 a series of stepping-stones. It must have been either a continent or 

 an archipelago. 



But a further and a peculiar interest attaches to this lost continent. 

 Those who have any acquaintance with geology know that the placental 

 Mammalia — that is, animals which are classed with such higher forms 

 of life as apes, cats, dogs, bears, horses, and oxen — appear very abruptly 

 with the incoming of the Tertiary period. Now, judging by analogy, 

 it is not likely that these creatures can have been developed out of 

 Mesozoic forms with anything like the suddenness of their apparent 



