2 HISTORY OF THE EUROPEAN FAUNA. 



All these animals have a wide range in other parts 

 of the world. In past times, before man began to 

 make observations on the geographical distribution of 

 birds and butterflies, or even before the appearance of 

 man in Northern Europe, they may have lived all 

 over the British Islands. For some reason or other 

 they are perhaps dying out or withdrawing towards 

 their original home, which may either be northward, 

 or to the east or south. If we had some clue as to 

 their former history from fossil evidence or, in other 

 words, if their remains had been preserved to us in 

 geological deposits, we should have less difficulty in 

 deciding this problem. But butterflies are scarcely 

 ever preserved in a fossil state, and birds very rarely. 

 We know little or nothing, therefore, of their past 

 history from direct evidence, and are obliged to trust 

 to indirect methods of research which will be indi- 

 cated later on. 



X^Mammals and Snails tell us their story more plainly. 

 * The bones of the former and the shells of snails are 

 easily preserved, and thus furnish us with the neces- 

 sary data as to their past history, for we find them 

 abundantly in most of the recent geological deposits. 

 Among the mammals of the British Islands there 

 are some instances of distribution which much 

 resemble those I have quoted. Thus the Arctic Hare 

 (Lepus variabilis] is in the British Islands confined to 

 Ireland and to the mountains of Scotland ; and if it 

 were not for the fact that its bones have been dis- 

 covered in a cave in the south-west of England, we 



