iQi^. Reviews. 9^ 



One cannot help doubting, all the same, whether Dr. Scharff does not 

 dismiss too curtly the idea of a discontinuous land-connection, though 

 it is true that such a connection would not fit in with his ingenious explan- 

 ation of the origin of the Ice Age. He seems to regard the bridges that 

 he draws as almost literal bridges — too slender and insubstantial to 

 deserve the name of continents, and unlikely, therefore, to have endured 

 long enough to undergo repeated modifications of area, which might bring 

 them more than once into connection with each of the neighbouring 

 continents, and yet never simultaneously touch both. It is, however, 

 inconceivable that strictly freshwater fishes, for instance, could cross the 

 space that separates Europe from America unless the intervening land 

 mass was of sufficiently large dimensions to include river-systems of its 

 own comparable in size with the river-systems of the other continents, 

 and capable of receiving as tributaries — though not necessarily at the 

 same time — and thus mingling the faunas of the rivers of both. Dr. 

 Scharff's argument seems to imply that his Eocene trans-Atlantic land- 

 bridge, which he uses to explain the extension of the range of some fresh- 

 water habitants, including the crayfishes, must have deserved the name 

 of a true continent, in which species may well have originated that were 

 carried at one time to America and another to Europe. And it is question- 

 able whether we ought to ignore the possibility of a similar intermediate 

 origin for some of the animals that Dr. Scharft" supposes to have travelled 

 direct by his Scotland-Iceland-Labrador bridge the whole way from 

 Europe to America, or vice versa. 



What, for instance, about Helix hortensis ? The singular thing about 

 that snail is that though so distinctly local in its supposed place of origin 

 on the European side of the Atlantic, it seems to turn up on nearly all 

 the fragments of the old land bridge, with a regularity that suggests that 

 it must have been much more densely distributed in the region now 

 submerged than it is known to have been in Europe proper. Found, as Dr. 

 Scharff describes, in the Shetland Islands, the Faroes, Iceland, southern 

 Greenland, and the islands of the north-east coast of North America, as 

 well as on " parts of the opposite mainland," it seems from its present 

 distribution to have been more thoroughly at home in the lost Atlantis 

 than in any other part of its range. Believers in the permanence of 

 oceanic basins will, no doubt, accuse Dr. Scharff of considerable ex- 

 travagance in the erection of unnecessary bridges for the transportation 

 of forms that may have been accidentally dispersed, or whose apparent 

 relationships to one another may not be so close as is supposed. But 

 the author's arguments on these points, though they will not carry con- 

 viction everywhere, are much too strong to be easily met. We may 

 question whether it is possible for him to draw the line where he does, 

 but that is mainly a question of detail. If it were only for the vast number 

 of facts presented in this volume, zoologists would be deeply indebted 

 to Dr. Scharff for the care he has bestowed in bringing it out. 



C. B. M. 



