Mendel 231 



any meaning apart from the other, although in practice as 

 well as in theory we can make distinctions that lead to better 

 control of processes. 



Mendel 



It was a contemporary of Darwin who, apparently with- 

 out knowing it, converted all the speculative thinking about 

 evolution into a scientific problem that permitted an attack 

 by experimental methods. Gregor Johann Mendel, an 

 Augustinian monk in an obscure abbey in Brixnn, set him- 

 self the task of finding out exactly how the numerous 

 characteristics existing among the varieties of the com- 

 mon or garden peas were transmitted from parent to off- 

 spring. In a short paper published in 1866, summarizing 

 nine or ten years of study, he said that he considered 

 the experimental approach the only correct one to use if 

 we are '^ to reach the solution of a question the impor- 

 tance of which cannot be overestimated in connection 

 with the history of the evolution of organic forms." His 

 own results and the subsequent elaboration of his method 

 by other workers have amply justified not only his con- 

 fidence in experimental research, but in his selection of 

 the problem of heredity as crucial in its bearing upon 

 evolution. 



The revolutionary element in Mendel's procedure con- 

 sisted in restricting his question to a unit small enough to 

 handle. The usual procedure has been for us to think of 

 variations or traits in a given species of plants or animals in 

 their totality. For example, we think of the difference be- 

 tween a spaniel and a hound in terms of spanielness or hound- 

 ness. We think of two varieties of apples or grapes also in 

 terms of the entire plant or fruit. Mendel analyzed the 

 varieties of peas into the single traits that he could distin- 

 guish. For example, some plants are tall and some are short. 

 Some have hairy stems, some have smooth stems. Some va- 

 rieties have white flowers, some have colored flowers. Some 

 seeds are green, some are yellow. Some seeds are smooth. 



