MENDELISM 175 



clear and definite information only when applied to 

 cases where clearly definable characters have distin- 

 guished the parental forms examined. This, however, 

 is in great part due to the fact that the experimental 

 method has hitherto been little used in dealing with 

 characters of a less definite nature. The science is 

 still in its infancy, and attention has naturally been 

 first paid to the simpler problems which it affords. 

 The difficulties of treatment which confront those who 

 would deal with highly variable characters and those 

 of a ' more or less ' nature are considerable, although 

 there is no reason for supposing that such problems are 

 insuperable. As we have seen, however, the majority 

 of characters which distinguish species or races from 

 one another appear to be of a perfectly definite descrip- 

 tion, so that the limitation just referred to is not so 

 serious as might appear at' first sight. The recent 

 revival of work upon the subject of inheritance by 

 the use of breeding methods has, as a matter of fact, 

 already been rewarded with results as valuable and 

 as clear as could possibly have been anticipated 

 results which are sufficient in themselves to show that 

 the discovery made by Mendel was of an importance 

 little inferior to those of a Newton or a Dalton. 



It is important to remember that every animal or 

 plant, which has come into existence in the ordinary 

 way through sexual generation, owes its individuality 

 to the mingled natures of two separate parents. The 

 following lines, in which the poet Goethe speaks of 

 his own hereditary endowment, have been quoted 

 more than once in this connection ; 



