10 



inherited the long axis, and those of 

 72 plants some the long and some the 

 short axis. 



In each of these experiments a cer- 

 tain number of the plants came con- 

 stant with the dominant character. For 

 the determination of the proportion in 

 which the separation of the forms with 

 the constantly persistent character re- 

 sults, the two first experiments are of 

 especial importance, since in these a 

 larger number of plants can be com- 

 pared. The ratios 1.93 to 1 and 2.13 to 1 

 gave together almost exactly the aver- 

 age ratio of 2 to 1. The sixth experi- 

 ment gave a quite concordant result; 

 in the others the ratio varies more or 

 less, as was only to be expected in view 

 of the smaller number of 100 trial 

 plants. Experiment 5, which shows the 

 greatest departure, was repeated, and 

 then, in lieu of the ratio of 60 and 

 40, that of 65 and 35 resulted. The 

 average ratio of 2 to 1 appears, there- 

 fore, as fixed with certainty. It is 

 therefore demonstrated that, of those 

 forms which possess the dominant 

 character in the first generation, two- 

 thirds have the hybrid-character, while 

 one-third remains constant with the 

 dominant character. 



The ratio of 3 to 1, in accordance 

 with which the distribution of the 

 dominant and recessive characters re- 

 sults in the first generation, resolves 

 itself therefore in all experiments into 

 the ratio of 2 : 1 : 1 if the dominant char- 

 acter be differentiated according to its 

 significance as a hybrid-character or 

 as a parental one. Since the members of 

 the first generation [F2I spring di- 

 rectly from the seed of the hybrids 

 [Fi], it is ?20iv clear that the hybrids 

 forvi seeds havifig one or other of the 

 two differ entiatifig characters, and of 

 these one-half develop again the hy- 

 brid foriJi, while the other half yield 

 plants which remain constant and re- 

 ceive the dominant or the recessive 



MENDEL 



characters [respectively^ in equal 

 numbers. 



the subsequent generations 

 [bredI from the hybrids 



The proportions in which the de- 

 scendants of the hybrids develop and 

 split up in the first and second genera- 

 tions presumably hold good for all sub- 

 sequent progeny. Experiments 1 and 2 

 have already been carried through six 

 generations, 3 and 7 through five, and 

 4, 5, and 6 through four, these experi- 

 ments being continued from the third 

 generation with a small number of 

 plants, and no departure from the rule 

 has been perceptible. The offspring of 

 the hybrids separated in each genera- 

 tion in the ratio of 2:1:1 into hybrids 

 and constant forms. 



If A be taken as denoting one of the 

 two constant characters, for instance 

 the dominant, a, the recessive, and Aa 

 the hybrid form in which both are 

 conjoined, the expression 



A + lAa + a 



shows the terms in the series for the 

 progeny of the hybrids of two differ- 

 entiating characters. 



The observation made by Gartner, 

 Kolreuter, and others, that hybrids are 

 inclined to revert to the parental forms, 

 is also confirmed by the experiments 

 described. It is seen that the number 

 of the hybrids which arise from one 

 fertilisation, as compared with the 

 number of forms which become con- 

 stant, and their progeny from genera- 

 tion to generation, is continually di- 

 minishing, but that nevertheless they 

 could not entirely disappear. If an 

 average equality of fertility in all plants 

 in all generations be assumed, and if, 

 furthermore, each hybrid forms seed 

 of which one-half yields h\'brids again, 

 while the other half is constant to both 

 characters in equal proportions, the 

 ratio of numbers for the offspring in 



