APPENDIX 351 



These in the second year of experiment are united again w illi the 

 pollen cells abcy and we obtain the series 



AaBbCc + AaBbc + AabCc + aBbCc + Aabc + ciBbc -f abCc + ahr. 



Since the form abc occurs once in the series of eight terms, it is 

 consequently little likely that it would be missing among the experi- 

 mental plants, even were these raised in a smaller number, and the 

 transformation would be perfected already by a second fertiHsa- 

 tion. If by chance it did not appear, then the fertilisation nuist })e 

 repeated with one of those forms nearest akin, Aabc, ciBhr, abCc. 

 It is perceived that such an experiment must extend the farther the 

 smaller the number of experimental plants and the larger the number 

 of differentiating characters in the two original species; and that, 

 furthermore, in the same species there can easily occur a delay of 

 one or even of two generations such as Gartner observed. The 

 transformation of widely divergent species could generally only l)e 

 completed in five or six years of experiment, since the numl)er of 

 different egg cells which are formed in the hybrid increases, as the 

 powers of two, with the number of differentiating characters. 



Gartner found by repeated experiments that the respective 

 period of transformation varies in many species, so that frec^uently 

 a species A can be transformed into a species B a generation sooner 

 than can species B into species A. He deduces therefrom that 

 Kolreuter's opinion can hardly be maintained that " the two 

 natures in hybrids are perfectly in equilibrium." It appears, how- 

 ever, that Kolreuter does not merit this criticism, but that Giirtner 

 rather has overlooked a material point, to which he himself else- 

 where draws attention, viz. that '* it depends which individual is 

 chosen for further transformation." Experiments which in this 

 connection were carried out with two species of Pisum demon- 

 strated that as regards the choice of the fittest indiAiduals for the 

 purpose of further fertilisation it may make a great difi'erence which 

 of two species is transformed into the other. The two experi- 

 mental plants differed in five characters, while at the same time 

 those of species A were all dominant and those of species B all 

 recessive. For mutual transformation .1 was fertilised with pollen 

 of B, and B with pollen of A, and this was repeated with both 



hybrids the following year. With the first experiment - there were 

 eighty-seven plants available in the third year of experiment for 



