THE FAUNA OF BRITAIN. IO5 



were similarly dealt with. All the more important 

 groups of animals are now being studied with a view 

 to determining their exact range in these islands. 

 Mr. Harvie-Brown, Mr. J. W. Taylor, Mr. Eagle Clarke, 

 Mr. Miller Christy, Mr. Ussher, Mr. Harrington, and 

 a number of others have considerably advanced our 

 knowledge in this direction in recent years. 



Any such contributions are to be welcomed as 

 furnishing us with the necessary data to solve the 

 problem of the origin of the British fauna. Mean- 

 while we know enough to enable us to assert 

 positively that the latter has reached us by land- 

 connections from various parts of Europe (cf. p. 35). 

 This statement of course refers to the bulk jgf the 

 Britishfauna^__The small proportion of indigenous 

 species, or such as have been introduced accidentally, 

 may be left out of consideration when dealing with 

 the great mass of animals which have evidently 

 migrated to the British Islands on land now sunk 

 beneath the sea (see Fig. 4, p. 60). Opinions of 

 zoologists, botanists, and geologists are practically 

 unanimous on this subject ; yet there are two other 

 theories, which have from time to time been advanced 

 to arrniini-fnrJJTej^i^itL^if thgJRrifrfch fauna. Only 



the first of these, however, can claim the serious 

 attention of those interested in the problem. Its 

 chief contention lies in the oft-asserted dictum of 

 the "imperfection of geological record" It has been 

 suggested, in fact, that the British fauna, instead 

 of having migrated to our islands, might have 



