210 THE ORIGIN OF SPECIES 



or only in a diirerciit section of the same order, (liifei- 

 greatly from each other. In both time and space the 

 lowly organized members of each class generally change 

 less than the highly organized; but there are in both 

 cases marked exceptions to the rule. According to our 

 theory, these several relations throughout time and space 

 are intelligible; for whether we look to the allied forms 

 of life which have changed during successive ages, or to 

 those which have changed after having migrated into dis- 

 tant quarters, in both cases they are connected by the 

 same bond of ordinary generation; in both cases the laws 

 of variation have been the same, and modifications have 

 been accumulated by the same means of natural selection 



