290 THE ORIGIN OF SPECIES 



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 ex- 

 posed to great changes of climate and have migrated 

 over great distances; whereas, in Egypt, during 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 de- 

 velopment, but is powerless against the doctrine of natu- 

 ral selection or the survival of the fittest, which implies 

 that when variations or individual differences of a ben- 

 eficial nature happen to arise, these will be preserved; 

 but this will be effected only under certain favorable 

 circumstances. 



The celebrated paleontologist, Bronn, at the close of 

 his German translation of this work, asks, how, on the 

 principle of natural selection, can a variet}' live side by 

 side with the parent species? If both have become 

 fitted for slightly different babits 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, etc., 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 also insists that distinct species never differ 

 from each other in single characters, but in many partsj 



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