No. 556] SHORTER ARTICLES AND DISCUSSION 



235 



The F 2 from self X albino should consequently contain Himalayans 

 as well as true albinos. But among the large number of animals reared 

 from such matings no Himalayans have hitherto been recorded, and for 

 the present the relations between these various forms remain obscure. 



If we suppose that albino may be either the second single re- 

 cessive or the double recessive we avoid this difficulty, but are 

 then unable to explain why albino X Himalayan should not, at 

 least occasionally, produce selfs by recombination. 



Now it seems to me that the facts of the case are fitted equally 

 well by either of two hypotheses. In the first place, we may con- 

 sider, as above, that Himalayan is a single recessive and albino a 

 double recessive — if we suppose the two factors concerned to be 

 completely linked. The gametic (not zygotic) constitution of 

 the three types would then be represented thus,' C being the color 

 producer and S the factor changing Himalayan to self. 



Self — CS 



Himalayan -Cs 

 Albino — cs 



If C and S be completely linked no cS individual can be ob- 

 tained, and CS X cs would give no Cs in F 2 . 



On the other hand, we may consider the factor for self as 

 allelomorphic to that for Himalayan pattern, and also to that for 

 albinism. Then the three pure types might be represented thus 

 (zygotic formulae) : 



Himalayan — HH 



8, H, and A being allelomorphic each to itself or to either of the 

 others, the crosses would result thus: 



