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THE AMERICAN NATURALIST [Vol. L 



peas from a certain pea plant and when these two kinds 

 were planted separately each continued to produce the 

 two kinds through four generations, that being as far as 

 the experiment was carried. In the light of the data I 

 present below his observations may be correct, he having 

 possibly secured one of the yellow forms such as I have 

 found. 



Mendel (1865) found when peas with yellow cotyledons 

 were crossed with green cotyledon forms that the first 

 generation offspring all had yellow cotyledons, but each 

 one of these yellow cotyledon F 1 plants produced F 2 

 seeds, approximately three fourths of which had yellow 

 cotyledons and one fourth green cotyledons. Either color 

 of parent could be used as the seed or female parent, and 

 the result was the same. Further, the F 2 greens in F 3 

 only produced greens, while the F 2 yellows when planted, 

 in some cases gave only yellows, in other cases both yel- 

 lows and greens in the proportion of 3 Y : 1 G. The actual 

 data by which Mendel supported these statements are as 

 follows : fifty-eight crosses on 10 plants were made, and 

 in every case, yellow was dominant to green in the F x 

 generation of these crosses. 258 F x plants produced 8,023 

 F 2 seeds of which 6,022 were yellow and 2,001 had green 

 cotyledons, an actual ratio of 75.1 yellow to 24.9 green or 

 3.01 Y : 1 G. Mendel is careful to call attention to the wide 

 variability in the ratio of yellows to greens when the F 2 

 peas of each F t plant are considered separately, the vari- 

 ation ranging from 32 Y : 1 G on one plant to 20 Y : 19 G 

 on another. Between these extremes, there were some 

 among the 10 F 2 plants of which he gives the ratios, that 

 closely approximated the theoretical 3:1 ratio. I call 

 attention to this great variability that Mendel found be- 

 cause some geneticists of late, apparently not having 

 noted that Mendel himself observed these same facts, 

 have referred to this as a new phenomenon. Only aver- 

 age ratios from large numbers were considered by Men- 

 del, as small numbers tended to obscure the significance 

 of the facts. Of the 8,023 F 2 seeds secured by Mendel, 



