OBJECTIONS TO THE THEORY 289 



unless they themselves likewise changed, and no one will 

 dispute that the physical conditions of each country, as 

 well as the numbers 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 bien- 

 nial plant or one of tbe lower animals might range into 

 a cold climate and perish there every winter; and yet, 

 owing to advantages gained through natural selection, 

 survive from year to year by means of its seeds or ova? 

 Mr. E. Ray Lankester has recently discussed this subject, 

 and he concludes, as far as its extreme complexity allows 

 him to form a judgment, that longevity is generally re- 

 lated to the standard of each species in the scale of 

 organization, as well as to the amount of expenditure 

 in reproduction and in general activity. And these con- 

 ditions have, it is probable, been largely determined 

 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 argu- 

 ment 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 pro- 

 duced through the modification of their original types. 



—Science — 13 



