294 Shull. 



(6) yO = '^. yy = cf (Gulick 1911. Hertwig 1912). 



(7) zO = ?, Z2 =0" (Hertwig 1912). 



5. The male is assumed to he a negative homozygote. 



Model formulae: XXFf = 9, XXff = cf, 



or simply, Ff = 9, ff= (f. 

 These formulae have been used by Spillma^^ (1908), GooD.AiE 

 (1909), Hurst (1909), Peabl and Surface (1910a, b), Morgan (1911a), 

 Bateson and Punnett (1911), Cole (1912), Morgan and Goodale 



(1912), HADLEY (1913), GOLDSGHMIDT (1913), and JOHANNSEN (1913). 

 Synonymous formulae : 



(1) Ffmm = ?, ffmm = cf (Morgan 1911a). 



(2) FO =9, 00 = cT (Morgan 1911a, Morgan and 



Goodale 1912). 



(3) FG =.9, GG = d" (Wilson 1910, Pinney 1911). 



(4) Z =9, no-X = cf (Castle 1909). 



(5) Z — =9, = cf (Castle 1912). 



(6) XO =9, 00 = cT (Morgan 1911a). 

 {!) xO = 9, 00 = cf (Hertwig 1912). 



(8) XO =9,0 = c^ (Pinney 1911). 



(9) XY = 9, YY = d (Wilson 1910, Morgan and 



Goodale 1912). 

 (10) xy = 9, yy = cf (Schleip 1912). 



6. The male is assumed to be a neutral homozygote. 



Model formulae: XXFM = 9, XXM3I = cT, 

 or simply, FM = 9, MM = cf. 



These formulae have been used by Federley (1911). 

 Synonymous formulae: 



(1) f(m) = 9, mm = c? (Schleip 1912). 



(2) 9cf = 9, cfcf = (f (Punnett and Bateson 1908, 



Doncaster 1908, Bateson 1909, Hurst 

 1909, Goodale 1910, Smith 1910, 1911, 

 1913, Morgan 1911a). 



(3) 9(cr) = 9, cTcf = cf (Wilson 1909). 



The .50 sets of foi'mulae here listed are not all that have been 

 used to represent these 6 fundamentally distinct ideas regarding the 

 genotypic interrelations of the sexes, but they are sufficient, I think, 

 to indicate the degree of simplification which would result from a general 



