56 THE EVOLUTION OF LIFE. 



Chicago. Out of these the reader may form a notion of the 

 theory : 



"Orthogenesis shows that organisms develop in definite directions 

 without the least regard for utility through purely physiological causes 

 as the result of organic growth, as I term the process. " 



' ' I am concerned in this paper with definitely directed evolution 

 as the cause of transmutation, and not with the effects of the use and 

 activity of organs which with Lamarck I adopted as the second main 

 explanatory cause thereof." 



"The causes of definitely directed evolution are contained, accord- 

 ing to my view, in the effects produced by outward circumstances and 

 influences such as climate and nutrition upon the constitution of a 

 given organism." 



"At variance with all the facts of definitely directed evolution 

 ... is also the contention of my opponent [Weismann] . . . 

 that the variations demonstrably oscillate to and fro in the most di- 

 verse directions about a given zero-point. There is no oscillation in 

 the direction of development, but simply an advance forwards in a 

 straight line with occasional lateral divergences whereby the forkings 

 of the ancestral tree are produced. " * 



These sentences contain one of those explanations which 

 explain nothing; for we are not enabled to see how the 

 " outward circumstances and influences " produce the effects 

 ascribed to them. We are not shown in what way they 

 cause organic evolution in general, still less in what way 

 they cause the infinitely-varied forms in which organic evo- 

 lution results. The assertion that evolution takes definitely- 

 directed lines is accompanied by no indication of the reasons 

 why particular lines are followed rather than others. In 

 short, we are simply taken a step back, and for further in- 

 terpretation referred to a cause said to be adequate, but the 

 operations of which we are to imagine as best we may. 



This is a re-introduction of supernaturalism under a dis- 

 guise. It may pair off with the conception made popular by 

 the Vestiges of the Natural History of Creation, in which it 

 was contended that there exists a persistent tendency towards 

 the birth of a higher form of creature ; or it may be bracketed 

 * " On Orthogenesis and the Impotence of Natural Selection in Species- 

 Formation," pp. 2, 19, 22, 24. 



