HIGHER PLANTS AND ANIMALS. 319 



to have differed during the past the lower being more per- 

 sistent, or less variable, than the higher so the same ratio 

 will manifest itself in the future, the more highly organised 

 passing by more rapid stages into newer and higher forms. 

 Within the same limit of time the invertebrate may un- 

 dergo less modification than the vertebrate, the aquatic less 

 than the terrestrial, and the cold-blooded less than the 

 warm-blooded ; but all (by whatever process) must sooner 

 or later pass into newer and higher forms, and man himself 

 as certainly as the plants and animals that form the theme 

 of his deliberations. If there exist a great Law of Progres- 

 sion and all that palaeontology has revealed of the past or 

 physiology taught of the present points to such an ordain- 

 ing it would be reversing our ordinary ideas of the per- 

 manence of nature to suppose such progression had come 

 to an end when all its accompaniments and all the media 

 through which it manifests itself remain unimpaired and 

 persistent. And it would be equally at variance with all 

 philosophical notions of natural history to suppose that a 

 law which had operated alike on all the orders of life in the 

 past would become partial and exempting in the present. 

 It may startle some minds to hear the same argument ap- 

 plied to man as to the rest of the animate creation. The 

 reverse, unfortunately, has been too long the fashion. The 

 interests of science, as well as the sacredness of truth, demand, 

 however, that where nature operates alike the student of 

 nature shall not venture to obtrude with artificial " schemes 

 of arrangement," and "lines of demarcation." Looking at 

 it merely as a question of natural history and this, be it 

 observed, is the only way in which science can approach it 

 the future of the human race must be subject to the 

 same laws of variation and progression as those which have 

 governed and still continue to govern the extinctions and 

 evolutions of the other orders of vitality. The rate of 



