330 MOSTLY MAMMALS 



between Southern Europe or Ireland, or between Ireland 

 and North America, seems altogether out of the question 

 within any period during which the fauna can have been 

 specifically identical with that of the present day. The 

 only conclusion is that from ancestors, presumably of the 

 same genus, which took to an underground life in such 

 widely separated localities, the similar conditions of the 

 caves have evolved descendants so similar that when com- 

 pared they cannot, or can hardly, be specifically distinguished 

 from each other." 



Should these identifications be confirmed, it will be evident 

 that the same, or closely allied species, have originated inde- 

 pendently in different caves, and although the author cited 

 is of opinion that this phenomenon may only hold good with 

 regard to cave-animals, it is possible that it may be found 

 also to exist in the outer world, since it has been suggested 

 that the horses (Equus) have originated independently in 

 the Old and New Worlds from different ancestral stocks. 



