18 LIFE ON THE EARTH. 



ascertained by the temperatures placed opposite the 

 several elevations. 



PROVINCES OF LIFE. 



We have been speaking of the climatal distribu- 

 tion of life-forms in general, and of the larger groups 

 and families. The distribution of genera and of species 

 seems to obey the same general laws of co-ordination 

 to climate, elevation, and depth ; but it also often 

 suggests the dependence on existing purely local 

 conditions, on ancient geological revolutions, or even 

 on locality considered alone and without regard to 

 conditions. 



The great group of Ferns occurs in nearly all 

 latitudes ; Arborescent Ferns, excluded from cold and 

 fluctuating climates, extend further to the south than 

 to the north of the equator. Thus, Aspidium is arbo- 

 rescent on the shores of Auckland and Campbell, as 

 far as 52^ S. Lat.;,Alsophila and Cybotium in Aus- 

 tralia and Van Diemen; Cyathea and Dicksonia are 

 conspicuous in the vegetation of New Zealand. 



An example of the limitation of a race to terres- 

 trial conditions is afforded by the Gorilla ; that mon- 

 strous anthropoid animal of the eastern coast of 

 Africa, whose residence seems limited by the forests 

 which supply it with food. 



On the contrary, it is to ancient geological revo- 



