Fitness in the Living World 3 l 



constitution and behavior of protoplasm and cells as well 

 as in the morphological and physiological modifications 

 which fit the organism to changed conditions of environ- 



r 



ment. 



So general are such adaptations that it has often been 

 asserted by naturalists and philosophers that they are uni- 

 versal that all structures, functions, and relations of living 

 things are adaptive or useful, or at least that they were 

 adaptive at the time of their origin, and that, with regard 

 to every vital process, we may properly ask the question, 

 cui bono, being confident that it is or has been useful. This 

 postulate of universal utility in the living world could be 

 maintained only by assuming that many things which are 

 now injurious had once been useful, and that many things 

 which now seem to be useless will sometime be found to 

 have a use. Such a postulate may be logically and hypo- 

 thetically possible, but it is very improbable. While there 

 are innumerable instances of utility in the living world, 

 there are thousands of cases where structures, functions, or 

 relations are in all probabilities not useful but indifferent, 

 and some cases, though relatively few, in which they are 

 positively injurious. Therefore it is not possible to maintain 

 the postulate of universal utility in the living world. 



Having found that general adaptability is universal in, 

 the living world but that success in making adaptations to 

 particular conditions is never perfect and is sometimes 

 lacking altogether, and that it is not safe to assume that 

 every structure, function, or relation of organisms confers 

 some known or unknown benefit upon its possessor, we may 

 proceed to examine in detail some of the more striking and 

 wonderful fitnesses which are found in the living world. 



In this survey, we shall deal not only with the general 

 relations of organisms to their environments but also with 



