244 Experimental Transformation of Species 



That is to say, if the dwarf green-seeded plants (for example, 

 the last in F2 of Fig. 61) were self -fertilized they would pro- 

 duce only dwarf green-seeded progeny. In the case of the 

 rodents, the white long-haired individuals which did not re- 

 semble either of the parents (who were black-haired hy- 

 brids) would always breed true for long hair and white coat. 

 Similarly the yellow-seeded dwarf would breed true for the 

 dwarf character, but not necessarily for the yellow seeds; and 

 the tall green-seeded plants would breed true, when self- 

 fertilized, for the green color of the seed but not necessarily 

 for tallness. 



Tri-hybrid 



Mendel continued his experiments with three traits — 

 for example, tallness, color of seed, and roundness or angu- 

 larity of the seed. In such crossings for three characters, 

 the law of dominance still held. That is, in the hybrid gen- 

 eration all the plants were tall, all produced yellow seeds and 

 all produced roundish or smooth seeds. On allowing these 

 hybrid plants, which presented the dominant character of 

 all the pairs studied, to fertilize themselves there was pro- 

 duced a generation in which each pair of characters was 

 segregated in the usual ratio of three dominants to one re- 

 cessive. Thus there were: 



3 tails to I dwarf, 



3 yellow-seeded to i green-seeded, 



3 smooth-seeded to i wrinkle-seeded. 



But there was further to be observed every possible com- 

 bination of three pairs of characters, namely eight (2^). 

 Furthermore, these new combinations appeared in definite 

 proportions, which can be stated in a simple mathematical 

 formula. The actual constitution of such a segregated hy- 

 brid generation for the three pairs of characters in question 

 is as follows for 64 individuals, the smallest number that can 

 show all the combinations: 



