356 



Eye-Colour in Gammarns 



inheritance of spots did not follow the simple Mendelian law. The 

 spotted condition did not behave either as a pure dominant or a pure 

 recessive. Spotted animals mated together always gave both spotted 

 and unspotted offspring. One point, however, came out clearly, namely, 

 that Albinos and coloured strains carrying Albino give a much larger 

 percentage of spotted young than do pure coloured strains. 



There is a possibility that the inheritance of spots follows some 

 more complicated Mendelian law, as will be seen from the figures for 

 a certain number of selected cases given below. The Mendelian ratios 

 3:1, 9:7, 15:1 frequently occur in some of the best cases we have, 

 where figures are large, but it is hard to find any consistent theory. 

 The reversal of the proportions given by experiments I.E. and I.E. So 

 is curious and may be significant. 



3. Selected Cases. 

 Matings o/Gammarus chevreuxi; all animals from "spotted" stock. 



B = Black, b = absence of Black, i.e. Red. 



C = Colour, c = absence of Colour, i.e. Albino. 



Figures for spotted include all spots, patches or streaks of white pigment. 



Red carrying Albino x Red carrying Albino Both spotted. 

 Ccbb X Ccbb 



Red carrying Albino x Albino carrying Red. Neither spotted 

 Ccbb X ccbb 



Unspotted Spotted Unspotted Spotted 



Red Red Albino Albino 



Family Cross 20. Expt. 100 18 66 38 



