420 



INSULAE FLOE AS AND FAUNAS WITH 



[Ch. XLI. 



Mr. Hartung found fragments of rock in the Azores wliicli lie 

 regarded as erratics or of iceborne origin. When^ indeed, 

 we consider all the changes in climate, and in the direction 

 of winds and currents, and in the species of birds which have 

 occurred in the lapse of millions of years since the Miocene 

 epoch, to say nothing of the incessant transformations under- 

 o-one by the volcanic islands themselves, we must feel that 

 the colonisation of the several archipelagos has been the 



com 



more 



anomalous or ca- 

 reasonably have 



animal 



the distribution of species is not 

 pricious in its character than we 

 anticipated. If we find a plant < 

 single island, we may suppose it to have been first brought 

 there as a straggler from the adjoining continent, and it may 

 never have been able to spread to any other island ; or it 

 may have had a wider range until dispossessed of most of its 

 former stations by new intruders, or by volcanic eruptions ; 

 or lastly, the parent stock may still flourish in some one of 

 the islands or archipelagos, but the descendants may have 

 gone on diverging from the original type, until, in the lapse 



millions of srenerations, the amount 



When 



of specific value. 



whether of plants or insects, 



common 



the Azores, 



Madeiras, and Canaries, it is only the genera which are 

 spoken of, for the species are almost always distinct in each 



r 



arcliipelago. 



Mr 



' Origin of Species,''^ tliat we 



remain ignorant of many means 



migration wliicli will one day be discovered. These antici- 

 pations have been singularly verified even since the appear- 

 ance of the last edition of bis celebrated work. Hearing that 

 many new plants bad been observed to spring np in Southern 

 Africa in districts which had been invaded by locusts, he 

 -nrocured from a correspondent, Mr. Weale, residing in Natal, 



small 

 an ounce. 



from the middle 



pellets, and their true nature ascertained by dissection, and 



» Chap. xi. 4th ed. p. 433. 1866. 



