Chat. VH.] THEORY OF NATURAL SELECTION. 263 



at apy one time perfectly adapted to their conditions of 

 life, ha\e remained so, when their conditions changed, 

 unless they themselves likewise changed; and no one 

 will dispute that the physical conditions of each country, 

 as well as the numhers and kinds of its inhabitants, have 

 undergone many mutations. 



A critic has lately insisted, with some parade of 

 mathematical accuracy, that longevity is a great advan- 

 tage to all species, so that he who believes in natural 

 selection " must arrange his genealogical tree " in such 

 a manner that all the descendants have longer lives than 

 their progenitors! Cannot our critic conceive that a 

 biennial plant or one of the lower animals might range 

 into a cold climate and perish there every winter; and 

 yet, owing to advantages gained through natural selec- 

 tion, survive from year to year by means of its seeds or 

 ova? Mr. E. Kay Lankester has recently discussed this 

 subject, and he concludes, as far as its extreme com- 

 plexity allows him to form a judgment, that longevity 

 is generally related to the standard of each species in 

 the scale of organisation, as well as to the amount of ex- 

 penditure in reproduction and in general activity. And 

 these conditions have, it is probable, been largely de- 

 termined through natural selection. 



It has been argued that, as none of the animals and 

 plants of Egypt, of which we know anything, have 

 changed during the last three or four thousand years, 

 so probably have none in any part of the world. But, 

 as Mr. G. H. Lewes has remarked, this line of argument 

 proves too much, for the ancient domestic races figured 

 on the Egyptian monuments, or embalmed, are closely 

 similar or even identical with those now living; yet all 

 naturalists admit that such races have been produced 

 19 



