v] Dominant and Recessive Whites 101 



The numbers were not sufficient to give the ratio 

 definitely, but it was established by subsequent breeding 

 that the whites bred true ; that the blues did not throw 

 blacks ; but some at least of the blacks could throw blues. 

 The blues breed true except in so far as they may throw 

 whites*. 



We have then the fact that a reversionary type was 

 produced, but that it did not appear till F^. The meaning 

 of this is obviously that the blue cannot appear in F^ 

 because black is epistatic to it. The elements necessary to 

 produce blue are all present in F^ but in it black also is 

 present which conceals the blue. After the re-combinations, 

 some F 2 forms contain the blue group of elements without 

 black, and these are therefore blue. We do not know in 

 this case that the Black Barb itself did not contain all that 

 is necessary to the production of blue, and it is thus possible 

 that the reversion on crossing may here be only a pheno- 

 menon of re-combination. This could only be decided by a 

 long statistical analysis. 



Genetic Properties of White Types which are not Albinos 

 (Fowls and Primula). Dominant and Recessive Whites. 



Albinism, namely total deficiency of colour, as we have 

 seen, is always recessive to the presence of colour f. In 

 contrast with real albinos, the white forms which contain 

 pigment in some part of their organisation show various 

 phenomena of colour-inheritance. Among both animals 

 and plants such types are known. For example, races of 

 pigs, cats, mice, cattle, dogs and fowls exist in which the 

 skin, hair or feathers are white, or nearly so, though the 

 eye is pigmented. The " white" races of mankind perhaps 

 belong to the same category in some respects. Our know- 

 ledge of the genetic behaviour of most of these types as 

 regards pigmentation is still fragmentary, but what little is 

 known points to the existence of considerable complications. 



Respecting white poultry, however, several features have 

 been ascertained which are interesting. In them we meet 



* Apparently only those blacks and blues which had some white 

 feathers were capable of throwing whites. 



t In Axolotl (see p. 43) an alleged exception is recorded. 



