THE METHOD OF EXPERIMENTAL BREEDING 



465 



recessive characteristic by R, the following summary of the possible 

 crosses can be made: 



(Parents) DD X DD 



(Parents) RR X RR 



(Parents) DD X RR- 



(Parents) DR X DR 



100 per cent DD (offspring) 

 100 per cent RR (offspring) 

 100 per cent DR (offspring) 

 25 per cent DD plus 50 per cent DR plus 

 25 per cent RR (offspring) 

 (Parents) DR X RR — 50 per cent DR plus 50 per cent RR (off- 

 spring) 

 (Parents) DR X DD — 50 per cent DR plus 50 per cent DD (off- 

 spring) 



It must be understood that large numbers of specific cases were 

 studied in order to obtain the percentages that have been indicated 

 as characteristic of these crosses. The table (Fig. 244) gives some 

 of the actual number of individuals in the F2 generatiftn in IVIendePs 

 original experiments. 



Fig. 244. — Data from Mendel's original experiments upon which was based 

 the 3 : 1 ratio characteristic of the F-i generation in mono-hybridization. 



(From Walter, 

 permission.) 



'Genetics," copyright, 1922, by The Macmillan Co., reprinted by 



Extension of Mendelian Theory. — Mendel published the results 

 of his studies in 1866, but they remained unknown until 1900, 

 when his paper was discovered by three scientists who had inde- 

 pendently reached the conclusions that he had so clearly stated. 

 Since that time, his results have been confirmed by experiments 



