GENETICS 



may be described as one which emphasized differences 

 and put up barriers that should keep the unlike apart, 

 at the same time allowing only "birds of a feather" 

 to flock together. It was a brave and successful 

 attempt to bring order out of chaos by classifying 

 the living world, and it served its purpose well until 

 Darwin's idea of half a century ago, that the origin 

 of all species is from preceding species, put an en- 

 tirely new face upon the whole matter. Organisms 

 of different species were found to be related to one 

 another, and even man could no longer escape ac- 

 knowledging his poor animal relations. As a conse- 

 quence, likenesses rather than differences thereafter 

 claimed the most attention. 



During the reconstruction of pihylogenetic trees, 

 which seized the imagination and became the prin- 

 cipal business of post-Darwinian biologists, "connect- 

 ing links," that is, the crotched sticks in the woodpile 

 of organisms, which had hitherto been largely dis- 

 carded, were most eagerly sought after. It was just 

 these scraggly sticks, that were neither trunk nor 

 limb-wood but combinations of both, which told the 

 story of continuity and were indispensable in building 

 up a reunited whole. 



As the analysis of the living world gradually came 

 to shift from species to individuals, it was shown that 

 individuals may be regarded simply as aggregates 

 of imit characters which may combine so variously 

 that it becomes more and more difficult to maintain 

 constant barriers of any kind between the groups of 

 individuals arbitrarily called "species." 



