2IO COOK 



None of the 200 offspring of one of the tailless birds was tail- 

 less, but in the progeny of a son of the same bird the tailless 

 character gained expression in the regular Mendelian propor- 

 tions. 



Complete Doininance [Mendeltsm). — Complete dominance, 

 or Mendelism, is a form of polar inheritance in which onl}' one 

 of the divergent parental characters (dominant) is expressed in 

 the conjugates, but the perjugates are like both parents in a 

 proportion of three to one. The parent organisms and gamete 

 parents are diverse with respect to the expression of one or more 

 definitely contrasted characters. The conjugates show the 

 divergent character of only one of the parents, which is called 

 the dominant. The perjugates are again diverse like the parent 

 organisms, but the expression of the divergent characters of the 

 organic parents is unequal, three-quarters having the dominant 

 character expressed in the conjugates, and one-quarter the 

 character which was recessive or abeyant in the conjugates. 

 Subsequent generations will continue to reproduce the latter, 

 three dominants to one recessive. Thus Mendelism might be 

 reckoned as a weaker form of sex-inheritance in which the 

 phenomenon of dominance interfered with a strict equality of 

 expression-polarities in the conjugate phases. 



The inferences which have been based on the differences of 

 proportion in the expression of the parental characters of the 

 so-called first and second generations of a Mendelian cross fall 

 to the ground as soon as we consider in sufficient detail the re- 

 productive processes by which they are produced. The two 

 generations have an entirely different relation to the original 

 organisms or to the gamete parents, but at the same time the 

 relation of the characters to each other is not different in the 

 generations, in spite of the difference of proportions. In the 

 conjugate generation all the organisms arise from combinations 

 of unlike gametes, while in the perjugate generation only half 

 of them represent such combinations. But all of these show 

 the phenomenon of dominance, quite as in the first generation. 

 The behavior of first generations proves to us that characters 

 may be expressed by polarity, or as reciprocals, instead of as 

 averages or resultants. If we admit the same possibility for 



