270 PROBOSCIDIA. 



concurs, however, with the localities of its most abundant 

 remains, in showing that, like the Rein-deer, the northern 

 extreme of the temperate zone was its metropolis. 



Attempts have been made to account for the extinction 

 of the race of northern Elephants by alterations in the 

 climate of their hemisphere, or by violent geological catas- 

 trophes, and the like extraneous physical causes. When we 

 seek to apply the same hypothesis to explain the appa- 

 rently contemporaneous extinction of the gigantic leaf- 

 eating Megatheria of South America, the geological phe- 

 nomena of that continent appear to negative the occurrence 

 of such destructive changes. Our comparatively brief ex- 

 perience of the progress and duration of species within the 

 historical period, is surely insufficient to justify, in every 

 case of extinction, the verdict of violent death. With re- 

 gard to many of the larger Mammalia, especially those 

 which have passed away from the American and Austra- 

 lian continents, the absence of sufficient signs of extrinsic 

 extirpating change or convulsion, makes it almost as rea- 

 sonable to speculate with Brocchi,* on the possibility that 

 species like individuals may have had the cause of their 

 death inherent in their original constitution, independently 

 of changes in the external world, and that the term of 

 their existence, or the period of exhaustion of the prolific 

 force, may have been ordained from the commencement of 

 each species. 



* Cited by Lyell, ' Principles of Geology,' (1835,) vol. iii. p. 104. 



