12 MENDELISM chap. 



botanists and zoologists have been devoted to the con- 

 struction of hypothetical pedigrees suggesting the various 

 tracks of evolution by which one group of animals or 

 plants may have arisen from another through a long con- 

 tinued process of natural selection. The result of such 

 work on the whole may be said to have shown that the 

 diverse forms under which living things exist to-day, and 

 have existed in the past so far as palaeontology can tell 

 us, are consistent with the view that they are all related 

 by the community of descent which the accepted theory 

 of evolution demands, though as to the exact course of 

 descent for any particular group of animals there is often 

 considerable diversity of opinion. It is obvious that all 

 this work has little or nothing to do with the manner in 

 which species are formed. Indeed, the effect of Darwin's 

 Origin of Species was to divert attention from the way in 

 which species originate. At the time that it was put 

 forward his explanation appeared so satisfying that bi- 

 ologists accepted the notions of variation and heredity 

 there set forth and ceased to take any further interest in 

 the work of the hybridisers. Had Mendel's paper ap- 

 peared a dozen years earlier it is difl&cult to believe that 

 it could have failed to attract the attention it deserved. 

 Coming as it did a few years after the publication of Dar- 

 win's great work, it found men's minds set at rest on the 

 problems that he raised and their thoughts and energies 

 directed to other matters. 



