THEOEY OF A PACIFIC CONTINENT 321 



survey is that the American and Asiatic forms related to one 

 another are in Asia mainly confined to the south-eastern 

 border generally, or to Japan. Australia, New Zealand and 

 New Guinea also possess a large number of species and genera 

 very closely allied to west American ones. These seem rarely 

 to extend further north in Asia than Japan. Are we to throw 

 a bridge across the Pacific ocean from Japan in order to find a 

 possible explanation of this former invasion of south Asiatic 

 and Australian types into western America, or does any other 

 theory meet all the facts of the case ? 



Since Dr. Augustus Gould * first mooted the hypothesis of 

 a former Pacific continent about sixty years ago, the idea has 

 been widely discussed by biologists and geologists. Mr. 

 Murray's f attention seems to have been first drawn to the 

 subject by the occurrence of the beetle Meristhus scrobinula 

 in Mexico and China, and by the presence of the mole Urotri- 

 chus in California and Japan. The Japanese and Californian 

 moles are no longer placed into the same genus, but no one 

 doubts that the American Neiirotrichus and Japanese Urotri- 

 chus are very nearly related to one another and that they 

 must have had a common ancestor. 



The supporters of the theory of the permanence of our great 

 ocean basins explain such cases by means of a former Bering 

 Strait land bridge, but, as already stated, the solution of this 

 problem must be sought elsewhere. That several of the pre- 

 mises on which the theory of the permanence of ocean basins 

 is founded are incorrect has been demonstrated (pp. 274 

 277). Darwin's theoretical considerations on the formation 

 of coral reefs and atolls, which demanded a long continued 

 subsidence of the mid-Pacific region, have been amply veri- 

 fied. To put his subsidence theory to a practical test Darwin 

 suggested that a boring should be made into one of the cores 

 of an atoll. Through the perseverance and energy of Pro- 

 fessor Sollas $ and Professor Edgworth David a boring on 

 Funafuti atoll was carried to a depth of one thousand one 

 hundred and fourteen feet, where cores were obtained showing 

 that the whole mass of rock was composed of pure coral. Since 



* Gould, A., " Remarks on Mollusks," p. 78. 



t Murray, A., " Geographical Relations of Coleopterous Faunas," p. 37. 

 J Sollas, W. J., "The Atoll of Funafuti." 

 L.A. Y 



