130 CIKCrMSTANCES FAVOURABLE TO THE [Chap. IV 



many competitors, will be those that Trill spread most 

 widelv, and will give rise to the greatest number of new 

 varieties and species. They will thus play a more im- 

 portant part in the changing history of the organic world. 

 In accordance with this view, we can, perhaps, under- 

 stand some facts which will be again alluded to in our 

 chapter on Geographical Distribution ; for instance, the 

 fact of the productions of the smaller continent of 

 Australia now yielding before those of the larger Europaeo- 

 Asiatic area. Thus, also, it is that continental produc- 

 tions have everywhere become so largely naturalised on 

 islands. On a small island, the race for life will have 

 been less severe, and there will have been less modifica- 

 tion and less extermination. Hence, we can understand 

 how it is that the flora of Madeira, according to Oswald 

 Heer, resembles to a certain extent the extinct tertiary 

 flora of Europe. All fresh-water basins, taken together, 

 make a small area compared with that of the sea or of the 

 land. Consequently, the competition between fresh- water 

 productions will have been less severe than elsewhere ; 

 new forms will have been then more slowly produced, and 

 old forms more slowly exterminated. And it is in fresh- 

 water basins that we find seven genera of Ganoid fishes, 

 remnants of a once preponderant order : and in fresh 

 water we find some of the most anomalous forms now 

 known in the world as the Ornithorhynchus and Lepido- 

 siren, which, like fossils, connect to a certain extent 

 orders at present widely sundered in the natural scale. 

 These anomalous forms may be called living fossils; they 

 have endured to the present day, from having inhabited 

 a confined area, and from having been exposed to less 

 varied, and therefore less severe, competition. 



To sum up, as far as the extreme intricacy of the 



