Reviews — Wallace's Island Life. 89 



"Why not try submersion ? He believes that a submersion to the 

 extent of nearly 2,000 feet destroyed much of the life of the British 

 Isles during the latter part of the Glacial epoch. And if a steady- 

 going continental island like Britain, with a pedigree of rocks equal 

 to any in the world, should have thus suifered, why not a volcanic 

 accuinulation in mid-ocean, presumably unstable by reason of its 

 composition ? It is true that Pico is 7,000 feet above the sea, though 

 this is very exceptional. 



But the submersion of an oceanic island is inconvenient, as this 

 might favour the notion of Atlantis. The zoological reasoning is, as 

 usual, admirable throughout the chapter. 



2. Recent continental islands. — " Great Britain is perhaps the most 

 typical example of a large and recent continental island now to be 

 found on the globe." All geologists are aware that the British 

 Islands rest upon the 100-fathom platform, which extends in a 

 sweep from the coast of Jutland round by Shetland and Ireland to 

 the south-west of France, and that a rise of less than half this depth 

 would join England to the continent. Mr. Wallace goes into the 

 question of the direct evidence that exists of this recent union, espe- 

 cially quoting the cases of the well-known submei-ged forests in 

 Cornwall, Devon and the Bristol Channel. Certainly the forest-bed 

 of Cromer, in Norfolk, also mentioned by him in this connexion 

 (p. 317), belongs to quite a different category, as this is a pre-glacial 

 forest bed, almost Pliocene in its character, and can afford very little 

 proof of our latest union with the continent, which " geologists are 

 all agreed was subsequent to the greatest development of the ice, 

 but probably before the cold epoch had wholly passed away." The 

 buried river channels in Scotland, far below the present sea-level, 

 and the discovery of fresh-water and littoral shells at considerable 

 depths off our coasts, are additional proofs of former elevation. On 

 the other hand, the well-known phenomena of Moel Tryfaen, and 

 elsewhere, are indications of a submergence which is, the author 

 states, in no small degree, the cause why our islands are so poor in 

 species, since sufficient time had not elapsed for immigration to have 

 been completed " before the influx of purely terrestrial animals was 

 again cut off." This would seem to imply also that the communi- 

 cation might not have been very wide. 



Amongst the higher animals no more than three species — all 

 birds — can be said to be peculiar, and, whilst Germany has ninety 

 species of land mammalia. Great Britain has forty, and Ireland 

 twenty-two. Possibly the respective areas of the three countries 

 may have something to do with this, but the same cannot be said of 

 the more slowly moving reptiles and amphibia, since Belgium has 

 twenty-two species and Ireland only four. We are much better off 

 in freshwater fishes, there being no less than fifteen peculiar, of 

 which ten are species of trout and charr restricted to certain lakes 

 in the British Isles. These local modifications are due to restricted 

 intercourse, and the result is the same as with the life of Oceanic 

 islands. The remainder of -this chapter (xvi.) deals with the insects, 

 land and fresh water shells and flora, and is full of highly interesting 

 matter. 



