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affect the subject, as a whole. Sometimes indeed they 

 become at once intelligible from the historical records 

 connected with them, proving that human agencies have 

 been at work acting as transporting media, within a 

 period comparatively recent ; whilst at others, the fact 

 of the creature having been endowed with self- diffusive 

 powers to an extravagant degree may succeed equally in 

 rendering the phenomena explicable. But, even where 

 neither of these solutions would seem to suffice, we 

 should still recollect that it is only in the mass that such 

 questions can be pronounced upon ; and that, con- 

 sequently, where we are able to discover a rule which is 

 for the most part adhered to, it is more philosophical to 

 conclude that the departures from it are the result of 

 special disturbing causes (whatsoever they may have 

 been), than to permit them to undermine our faith in 

 what would be otherwise universally true. Thus, the 

 botanist tells us of Ixias, Stapelias, Mesembrianthe- 

 mums, Pelargoniums, and Euphorbias, as concentrated 

 in Southern Africa ; of Magnolias in Central America ; 

 of Calceolarias on the Andes; of Myrtles, Banksias, 

 Mimosas, and Eucalypti, in Australia ; and of the 

 Bread-fruit Trees in the South Sea Islands : the orni- 

 thologist points, inter alia, to the Toucons and Hum- 

 ming-Birds from South America and the West Indies ; 

 whilst the student of the higher animals informs us of 

 the Kangaroos (indeed of the whole of the subclass 

 Marsupialia, except the genus Didelphys) as peculiar to 

 Australia and a few islands to the north of it ; of Lemur 



