5 6 THE POPULAR SCIENCE MONTHLY. 



elude all the ideas associated with the words life and death, we find that 

 the sole facts known to us are that there go on in the plant certain inter- 

 dependent processes, in presence of certain aiding and hindering influ- 

 ences outside of it ; and that in some cases a difference of structure or 

 a favourable set of circumstances, allows these inter-dependent pro- 

 cesses to go on for longer periods than in other cases. Again, in the 

 working together of those many actions, internal and external, which 

 determine the lives or deaths of organisms, we see nothing to which 

 the words fitness and unfitness are applicable in the physical sense. If 

 a key fits a lock, or a glove a hand, the relation of the things to one 

 another is presentable to the perceptions. No approach to fitness of 

 this kind is made by an organism which continues to live under certain 

 conditions. Neither the organic structures themselves, nor their indi- 

 vidual movements, nor those combined movements of certain among 

 them which constitute conduct, are related in any analogous way to 

 the things and actions in the environment. Evidently the word fittest, 

 as thus used, is a figure of speech ; suggesting the fact that amid sur- 

 rounding actions, an organism characterized by the word has either a 

 greater ability than others of its kind to maintain the equilibrium of 

 its vital activities, or else has so much greater a power of multiplica- 

 tion that though not longer lived than they, it continues to live in pos- 

 terity more persistently. And indeed, as we here see, the word fittest 

 has to cover cases in which there may be less ability than usual to sur- 

 vive individually, but in which the defect is more than made good by 

 higher degrees of fertility. 



I have elaborated this criticism with the intention of emphasizing 

 the need for studying the changes which have gone on, and are ever 

 going on, in organic bodies, from an exclusively physical point of view. 

 On contemplating the facts from this point of view, we become aware 

 that, besides those special effects of the co-operating forces which 

 eventuate in the longer survival of one individual than of others, and 

 in the consequent increase through generations, of some trait which 

 furthered its survival ; many other effects are being wrought on each 

 and all of the individuals. Bodies of every class and quality, inorganic 

 as well as organic, are from instant to instant subject to the influences 

 in their environments ; are from instant to instant being changed by 

 these in ways that are mostly inconspicuous ; and are in course of time 

 changed by them in conspicuous ways. Living things in common with 

 dead things, are, I say, being thus perpetually acted upon and modi- 

 fied ; and the changes hence resulting, constitute an all-important part 

 of those undergone in the course of organic evolution. I do not mean 

 to imply that changes of this class pass entirely unrecognized ; for, as 

 we shall see, Mr. Darwin takes cognizance of certain secondary and 

 special ones. But the effects which are not taken into account, are 

 those primary and universal effects which give certain fundamental 

 characters, to all organisms. Contemplation of an analogy will best 



