ErjMINATION AND SELECTION. 



279 



ovor tlio ])roy. Under this bead may bo taken the plie- 

 nomena of parasitism. Neither cattle, nor horses, nor dogs 

 have ever run wild in Paraguay, owing to the insidious 

 attacks of a certain fly, which lays her eggs in the bodies of 

 the newly born. There is scai'oely a form of life so harmless 

 or so retiring as not to be liable to the attacks of enemies 

 from without or fi-om within. Among human folk, more- 

 over, elimination l)y enemies is not wholly unknown; and 

 in this connection it is a sad reflection, as Sir W. R. Grove 

 has well said, that man is almost the only animal that 

 tiglits, not for food, oi- means of life, or of perpetuating 

 its race, but from motives of merest vanity, ambition, or 

 passion. 



Kliiniiiation by competition is by far the most important. 

 As Mr. Darwin so well points out, the competition is keenest 

 between members of the same group and among individuals 

 of the same species, or between different groups or different 

 species which have, so to speak, similar aims in life. Alter- 

 nations of hard times and good times are liere effective, and 

 may convert competition into war. During the Exhibition 

 at iSoutli Kensington there were good times for rats. But 

 wlien the show was over, there followed times that were 

 cruelly hard. The keenest competition for the scanty food 

 ai'ose ; and the poor creatures were forced to prey upon 

 each other. "Their cravings for food," we voad m Nature, 

 " culminated in a fierce onslaught upon one another, which 

 was evidenced by the piteous cries of those being devoured. 

 Tlieir method of seizing their victims is to suddenly mako 

 a raid upon one weaker or smaller than themselves, and 

 after overpowering it by numbers, to tear it in pieces." 



During the upheavals and depressions and the marked 

 climatic changes of geological times, this alternation must 

 have occurred again and again. Not only would there be 



