i.j VARIATION AND HEREDITY 77 



doctrine, the American naturalist Cope. 1 Neo-Lamarckism 

 is therefore, of all the later forms of evolutionism, the only 

 one capable of admitting an internal and psychological 

 principle of development, although it is not bound to do 

 so. And it is also the only evolutionism that seems to 

 us to account for the building up of identical complex 

 organs on independent lines of development. For it is 

 quite conceivable that the same effort to turn the same 

 circumstances to good account might have the same result, 

 especially if the problem put by the circumstances is such 

 as to admit of only one solution. But the question re- 

 mains, whether the term "effort" must not then be taken 

 in a deeper sense, a sense even more psychological than 

 any neo-Lamarckian supposes. 



For a mere variation of size is one thing, and a change 

 of form is another. That an organ can be strengthened 

 and grow by exercise, nobody will deny. But it is a long 

 way from that to the progressive development of an eye 

 like that of the molluscs and of the vertebrates. If this 

 development be ascribed to the influence of light, long 

 continued but passively received, we fall back on the theory 

 we have just criticized. If, on the other hand, an internal 

 activity is appealed to, then it must be something quite 

 different from what we usually call an effort, for never 

 has an effort been known to produce the slightest com- 

 plication of an organ, and yet an enormous number of 

 complications, all admirably coordinated, have been 

 necessary to pass from the pigment-spot of the Infusorian 

 to the eye of the vertebrate. But, even if we accept this 

 notion of the evolutionary process in the case of animals, 

 how can we apply it to plants? Here, variations of form 

 do not seem to imply, nor always to lead to, functional 



» Cope, The Origin of the Fittest, 1887; The Primary Factors of Organic 

 Evolution, 1896. 



