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THE AMERICAN NATURALIST [Vol. XL VI 



operation in the genesis of new characters and in the 

 adaptive trends of allometric evolution without gaining 

 any intimate knowledge of what the causes are. This 

 thought may be made clear through the following anal- 

 ogy. Naturalists observed and measured the rise and 

 fall of the tides long before Newton discovered the law 

 of gravitation; we biologists are simply observing and 

 measuring the rise and fall of the greater currents of 

 life. It is possible that a second Darwin may discover 

 a law underlying these phenomena bearing the same re- 

 lation to biology that the law of gravity has to physics, 

 or it is possible that such law may remain forever un- 

 discovered. Another analogy may make our meaning 

 still clearer. Ontogenesis is inconceivable, for example, 

 the transformation of an infinitesimal speck of fertilized 

 matter into a gigantic whale or dinosaur ; we may watch 

 every step in the process of embryogeny and ontogeny 

 without becoming any wiser; in a similar sense phylo- 

 genesis may be inconceivable or beyond the power of 

 human discovery. Not that we accept Driesch's idea of 

 an entelechy or Bergson's metaphysical projection of 

 the organic world as an individual, because we must be- 

 lieve that the entire secret of evolution and adaptation 

 ' is wrapped up in the interactions of the four relations 

 that we know of, namely, the germinal, the bodily, the 

 environmental, with selection operating incessantly as 

 the arbiter of fitness in the results produced. In the 

 meantime 40 we paleontologists have made what appears 

 to be a substantial advance in finding ever more con- 

 vincing evidence of the operation of law rather than of 

 chance in the origin and development of new characters, 



