MENDEL'S LIFE AND WORK 23 



again without the slightest change in the individuals 

 of the succeeding generations. 



The third idea introduced by Mendel, and about 

 the originality of which there cannot be the slightest 

 doubt, was that of keeping separate records of the 

 results obtained from every individual seed pro- 

 duced. So important is this, that it is quite certain 

 Mendel would never have formulated the law which 

 now bears his name if he had not adopted this method 

 of work. The number of forms which the progeny 

 of the hybrids between different races can assume 

 and the numerical ratios existing between them can 

 be ascertained only by this laborious method, and 

 without a knowledge of these ratios there can be no 

 certainty about the hereditary factors involved in 

 any particular case. 



5. The Great Result of Mendel's Work on 

 Heredity — Mendel's Law. 



In order to show quite clearly the outstanding 

 result of Mendel's work, namely, the formulation of 

 what is now known as Mendel's Law, it will be well 

 to refer very briefly to a few facts connected with 

 his experiments with peas. 



After some preliminary trials, devoted mainly to 

 testing the purity of the varieties of peas with 

 which he proposed to work, Mendel selected seven 

 pairs of differentiating characters for observation. 

 As examples of these may be cited : — 



Ripe seeds round and smooth, or nearly so. [ 

 „ ,, angular and deeply wrinkled. J 



