308 Problems of Organic Adaptation 



machine of human invention which had the power not only 

 to do the work for which it was devised but also to give 

 rise indefinitely to other machines of the same sort I Noth- 

 ing could illustrate more clearly the fundamental difference 

 between the living and the lifeless machine than this power 

 of reproduction. If reproduction is one of the fundamental 

 and original properties of living things and is therefore 

 not to be explained as a result of organic evolution, at least 

 the innumerable adaptations for promoting reproduction 

 have arisen in the course of evolution and demand an ex- 

 planation. Among these are the differentiations of male 

 and female sex cells and all the differences in structure, 

 functions, and instincts between males and females; the 

 remarkable contrivances for insuring cross fertilization in 

 plants and animals and for preventing hybridization of 

 species; the infinite variety and nicety of the means for the 

 protection and nourishment of the young. Nothing in the 

 whole world of living things is more wonderful than these 

 adaptations for reproduction. 



Consider the wonderful fitness of the nervous system for 

 receiving and transmitting stimuli and for coordinating the 

 multitudinous activities of animals. The timer of an auto- 

 mobile is no more perfect than the timing of the various 

 contractions in the heart beat, and the timing of various 

 muscular contractions in standing or walking and much 

 more in talking or in playing any game such as tennis 

 or baseball is vastly more complex and perfect than in any 

 lifeless machine. Think of the fitness of every organ for 

 its particular use and then consider the peculiar fitness with 

 which these organs are coordinated into an harmonious 

 whole. 



Think of the variety and range of sensations in any higher 

 animal and the admirable fitness of the sense organs: the 



