NATURAL SELECTION 97 



facta which will be again alluded to in our chapter on 

 geographical distribution ; for instance, that the pro- 

 ductions of the smaller continent of Australia have 

 formerly yielded, and apparently are now yielding, 

 before those of the larger Europaeo-Asiatic area. Thus, 

 also, it is that continental productions 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 modification and less exter- 

 mination. Hence, perhaps, it comes that the flora of 

 Madeira, according to Oswald Heer, resembles 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 ; and, consequently, the com- 



ftetition between fresh-water productions will have been 

 ess severe than elsewhere ; new forms will have been 

 more slowly formed, and old forms more slowly ex- 

 terminated. And it is in fresh water that we find seven 

 genera of Ganoid fishes, remnants of a once pre- 

 ponderant order : and in fresh water we find some of 

 the most anomalous forms now known in the world, 

 as the Ornithorhynchus and Lepidosiren, which, like 

 fossils, connect to a certain extent orders now widely 

 separated in the natural scale. These anomalous forms 

 may almost be called living fossils ; they have endured 

 to the present day, from having inhabited a confined 

 area, and from having thus been exposed to less severe 

 competition. 



To sum up the circumstances favourable and un- 

 favourable to natural selection, as far as the extreme 

 intricacy of the subject permits. I conclude, looking 

 to the future, that for terrestrial productions a large 

 continental area, which will probably undergo many 

 oscillations of level, and which consequently will exist 

 for long periods in a broken condition, is the most 

 favourable for the production of many new forms of 

 life, likely to endure long and to spread widely. For 

 the area first existed as a continent, and the inhabitants, 

 at this period numerous in individuals and kinds, will 

 have been subjected to very severe competition. Wheo 



H 



