Chap. VII.] THEORY OF NATURAL SELECTION. 169 



gained through natural selection, survive from year to year by 

 means of its seeds or ova? Mr. E. Eay Lankester Las 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 expenditure in reproduction and in 

 general activity. And these conditions 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 

 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 through the modification of their 

 original types. The many animals which have remained unchanged 

 since the commencement of the glacial period, would have been an 

 incomparably stronger case, for these have been exposed to great 

 changes of climate and have migrated over great distances ; whereas, 

 in Egypt, daring the last several thousand years, the conditions of 

 life, as far as we know, have remained absolutely uniform. The 

 fact of little or no modification having been effected since the 

 glacial period would have been of some avail against those who 

 believe in an innate and necessary law of development, but is 

 powerless against the doctrine of natural selection or the survival 

 of the fittest, which implies that when variations or individual 

 differences of a beneficial nature happen to arise, these will be 

 preserved ; but this will be effected only under certain favourable 

 circumstances. 



The celebrated palajontologist, Bronn, at the close of his German 

 translation of this work, asks, how, on the principle of natural 

 selection, can a variety live side by side with the parent-species ? 

 If both have become fitted for slightly different habits of life or 

 conditions, they might live together ; and if we lay on one side 

 polymorphic species, in which the variability seems to be of a 

 peculiar nature, and all mere temporary variations, such as size, 

 albinism, &c, the more permanent varieties are generally found, as 

 far as I can discover, inhabiting distinct stations, — such as high 

 land or low land, dry or moist districts. Moreover, in the case of 

 animals which wander much about and cross freely, their varieties 

 seem to be generally confined to distinct regions. 



Bronn a' so insists that distinct species never differ from each other 



