226 CAUSES OF EXTIXCTION. 



cies first become rare and then extinct — if the too 

 rapid increase of every species, even the most fa- 

 voured, is steadily checked, as we must admit, 

 though how and when it is hard to say — and if we 

 see, without the smallest surprise, though unable 

 to assign the precise reason, one species abundant 

 and another closely-allied species rare in the same 

 disti'ict, why should we feel such great astonish- 

 ment at the rarity being caiTied a step further to 

 extinction ? An action going on on eveiy side of 

 us, and yet barely appreciable, might surely be car- 

 ried a little further without exciting our observa- 

 tion. Who would feel any great surprise at hear- 

 ing that the jMegalonyx was fonnerly rare com- 

 pared with the Megatherium, or that one of the 

 fossil monkeys was few in number compared -with 

 one of the now living monkeys ? and yet in this 

 comparative rarity we should have the plainest ev- 

 idence of less favourable conditions for their exist- 

 ence. To admit that species generally become rare 

 before they become extinct — to feel uo sui"prise at 

 the comparative rarity of one species with another, 

 and yet to call in some extraordinary agent and 

 to mai-vel gi-eatly when a species ceases to exist, 

 appears to me much the same as to admit that sick- 

 ness in the individual is the prelude to death — to 

 feel no surprise at sickness — but when the sick 

 man dies, to wonder, and to believe that he died 

 through violence. ■ , 



