f)98 THE AMERICAN NATURALIST [Vol. LI 



Corresponding to the excess of recessive segregates, a 

 deficiency of dominant homozygotes among dominant seg- 

 gregates was also noticed. Among 153 families derived 

 from fertile plants in the experiment above mentioned, 40 

 families were uniformly fertile, the remaining 113 fami- 

 lies showing segregation. The foniier, therefore, is 26.14 

 per cent, of the total number of families, and shows 

 7.19 per cent deficiency from the theoretically expected 

 percentage, 33.33 per cent., the probable error being 

 ± 2.68 per cent. 



In conclusion it may be stated that the allelomorphs 

 concerned in this investigation are probably subject to 

 reversible transformations, and that the probable fre- 

 quency of the allelomorphic transformation may be prac- 

 tically constant in a certain strain, and possibly may be 

 different in different strains. As to the conditions under 

 which such allelomorphic transformations take place, 

 nothing is yet certain except that these conditions are of 

 a hereditary nature. The manner in which different in- 

 tensities of allelomorphic transformations are inherited 

 will be the subject of further investigation. 



A word may be added here regarding the conception 

 of dominance and recessiveness. Bateson's theory of 

 "presence and absence of factors" is sometimes under- 

 stood in the sense that the dominant allelomorph is re- 

 garded as due to the real presence of an hereditary mate- 

 rial unit which is absent in the recessive allelomorph. 

 Such a conception is not in full accordance with the idea 

 of the reversible transformability of allelomorphs as de- 

 scribed in this investigation. There is another possibility 

 of the nature of allelomorphs. The dominant and the re- 

 cessive allelomorphs may be supposed to represent two 

 alternative conditions or phases of a single hereditary 

 substance, somewhat resembling the chemical conception 

 of polymerization. Consequently, the interchangeability 

 between the dominant and recessive allelomorphs is not 

 improbable theoretically. 



August 26, 1917 



