62 TERRESTRIAL ADAPTATIONS. 



in a direction very nearly north-east and south- 

 west, while the line of equal temperature is nearly 

 east and west. And the spontaneous growth or 

 advantageous cultivation of other plants, is in like 

 manner bounded by lines of which the course 

 depends upon very complex causes, but of which 

 the position is generally precise and fixed. 



CHAPTER VII. 



The Variety of Organization corresponding to 

 the Variety of Climate. 



THE organization of plants and animals is in dif- 

 ferent tribes formed upon schemes more or less 

 different, but in all cases adjusted in a general 

 way to the course and action of the elements. 

 The differences are connected with the different 

 habits and manners of living which belong to 

 different species ; and at any one place the vari- 

 ous species, both of animals and plants, have a 

 number of relations and mutual dependences 

 arising out of these differences. But besides the 

 differences of this kind, we find in the forms of 

 organic life another set of differences, by which 

 the animal and vegetable kingdom are fitted for 

 that variety in the climates of the earth, which 

 we have been endeavouring to explain. 



The existence of such differences is too obvious 

 to require to be dwelt upon. The plants and 



