DARWIN 



directly at London from the star Alpha Centauri; if, 

 at a point near the beginning of its journey, a very 

 minute force deflected its path by so small an amount 

 that, after a quarter of a million miles, it is still only 

 an inch out of its original course, yet this minute de- 

 flection would ultimately make the bullet miss the 

 Earth altogether. He then concludes that a single 

 minute change in a germ would ultimately make a 

 huge difference in the offspring after countless gen- 

 erations. He adds that "the application is at once ob- 

 vious.""' It is obvious, and the conclusion is that he 

 is absolutely wrong and makes an argument which 

 proves just the converse. The original direction of the 

 path of the bullet represents the line of offspring 

 which maintains exactly the same characteristics as 

 its ancestor : that is, a fixed species. At a certain time 

 let the species produce an extra inch in length of neck; 

 this corresponds to the point of deflection of the 

 bullet which then continues in a straight line in the 

 constant new direction, and this new direction corre- 

 sponds to a new fixed species with this extra inch in 

 length. The mathematical and graphical representa- 

 tion of the descendants of a fixed species is a straight 

 line ; each new change in a species must be shown by a 

 new change of direction of the straight line. To rep- 

 resent continuous small and progressively increasing 

 changes of a species, as are assumed by the Darwin- 

 ians, we must draw a line which is continually chang- 



22 Trans., Fhil, Zool., p. li. 



C 223 ] 



