386 



W. Batesuii. 



The simple F,. 3 Grey: 1 Albino is then regarded as the result 

 of crossing- grey with an Albino bearing- G.B. and Gh. The more 

 complex case 9 grey : 3 black : 3 albino is produced by crossing- grey 

 with an albino bearing g, B, C"h. Similarly by using an albino bearing 

 g, b, Ch, chocolates will appear in F.^. In fact the appearance in F.^ 

 of any of the "lower*' coulours shows that the albino used to produce 

 Fj was wanting in all the determiners "higher" than the one which 

 causes that colour to appear. A tabular representation of this system 

 will at once demonstrate the point. For example take F., 9 grey : 

 3 black : 4 albino. The parents are grey (CGB) and albino (cgB), 

 B being common to both (Fig. 14). 



Fig. 14. Diagram showing the F.2 result from the cross betiveen a grey rabbit or 



mouse having the gametic composition CgB and an albino having the composition 



CgB. The result is 9 greys : 3 blacks : 4 albinos. 



A positive proof that this system is a correct representation of 

 the facts will be obtained by studying the results of crossing grej' 

 with chocolate. The F« should then consist of 12 grey : 3 black : 

 1 chocolate. Of course the 12 grey will really consist of 9 greys 

 with the black determiner, and 3 greys without it, but the distinction 

 between these two types may not be easy to recognize. The appea- 

 rance of the hiadcs in this cross will be the critical point. 



