Chap. XI.] EXTINCTION. 97 



and rarer, and finally extinct ; — its place being seized 

 on by some more successful competitor. 



It is most difficult always to remember that the in- 

 crease of every creature is constantly being checked 

 by unperceived hostile agencies ; and that these same 

 unperceived agencies are amply sufficient to cause rarity, 

 and finally extinction. So little is this subject under- 

 stood, that I have heard surprise repeatedly expressed 

 at such great monsters as the Mastodon and the more 

 ancient Dinosaurians having become extinct ; as if mere 

 bodily strength gave victory in the battle of life. Mere 

 size, on the contrary, would in some cases determine, as 

 has been remarked by Owen, quicker extermination-from 

 the greater amount of requisite food. Before man in- 

 habited India or Africa, some cause must have checked 

 the continued increase of the existing elephant. A 

 highly capable judge, Dr. Falconer, believes that it is 

 chiefly insects which, from incessantly harassing and 

 weakening the elephant in India, check its increase ; and 

 this was Brace's conclusion with respect to the African 

 elephant in Abyssinia. It is certain that insects and 

 blood-sucking bats determine the existence of the larger 

 naturalized quadrupeds in several parts of S. America. 



We see in many cases in the more recent tertiary for- 

 mations, that rarity precedes extinction ; and we know 

 that this has been the progress of events with those 

 animals which have been exterminated, either locally or 

 wholly, through man's agency. I may repeat what I 

 published in 1845, namely, that to admit that species 

 generally become rare before they become extinct — to feel 

 no surprise at the rarity of a species, and yet to marvel 

 greatly when the species ceases to exist, is much the same 

 as to admit that sickness in the individual is the fore- 



