THE DISTRIBUTION OF ANIMALS AND PLANTS 409 



stragglers, so that only eighteen are permanent residents. Of 

 these birds fifteen are common European or African species, 

 which must have flown to the islands, or have been drifted 

 thither in storms. Of the remaining three, two are found also 

 in Madeira and the Canaries, and therefore may reasonably 

 be supposed to have been derived from Africa. One only is 

 regarded as peculiar to the Azores, and this is a bullfinch, so 

 nearly related to the European bullfinch that it may be regarded 

 as merely a local variety. Wallace accounts for these facts by 

 supposing that the Azores were depopulated by the cold of the 

 Glacial age, and that all these birds have arrived since that 

 time. There is, however, little probabiUty in such a supposi- 

 tion. He further supposes that fresh supplies of stray birds 

 from the mainland, arriving from time to time, have kept up 

 the identity of the species. Instead of evolution assisting him, 

 he has thus somewhat to strain the facts to agree with that 

 hypothesis. Similar explanations are given for the still more 

 remarkable fact that the land plants of the Azores are almost 

 wholly identical with European and African forms. The in- 

 sects and the land snails are, however, held to indicate the 

 evolution of a certain number of new specific forms on the 

 islands. The beetles number no less than 212 species, though 

 nearly half of them are supposed to have been introduced by 

 man. Of the whole number 175 are European, 19 are found 

 in Madeira and the Canaries, 3 are American. Fourteen 

 remain to be accounted for, though most of these are closely 

 allied to European and other species ; but a few are quite dis- 

 tinct from any elsewhere known. Wallace, however, very truly 

 remarks that our knowledge of the continental beetles is not 

 complete ; that the species in question are small and obscure ; 

 that they may be survivors of the Glacial period, and may thus 

 represent species now extinct on the mainland ; and that for 

 these reasons it may not be irrational to suppose that these 

 peculiar insects either still inhabit, or did once inhabit, some 



