THE GENETICS OF THE DUTCH RABBIT— A REPLY. 



By W. E. CASTLE. 



Professor Punnett has honoured me by reviewing in this Journal^ 

 my paper on the inheritance of white spotting in Dutch rabbits. His 

 own studies of the same subject have led him to suggest an interpreta- 

 tion of the results, which I have reported, somewhat different from my 

 own. I wish to point out that the two interpretations differ less in 

 substance than the casual reader might suppose, and to indicate what 

 are the essential differences and why preference should be given to one 

 interpretation rather than the other. 



Professor Punnett has described accurately the essential facts observed. 

 Three races of Dutch rabbits were found to breed true (within limits), 

 each to a different modal condition of the same general type of white 

 spotting. Punnett himself has observed three similar races, though 

 they were perhaps not identical with mine. Upon crossing the races 

 one with another, or with unspotted rabbits, Fi individuals were obtained 

 which were either intermediate in amount of white spotting or more 

 nearly resembled the darker parent. In F^, segregation of the original 

 types occurred, but with evidences of modification, the recovered types 

 been less divergent than those which entered the cross. So much as to 

 the facts agreed upon. Now as to the interpretation, I have assumed that 

 the segregation is of a monohybrid sort involving in each cross one 

 principal pair of allelomorphic factors and that the " mutual modifica- 

 tion" of types seen in F2 is due to "residual heredity." Punnett 

 objects to the assumption of modification and to the term residual 

 heredity, unless it is understood in both cases that factorial recombina- 

 tion is meant rather than factorial modification. I am quite ready to 

 concede the point. I used the expression " residual heredity " to cover 

 the unanalyzed genetic agencies responsible for the observed modification 

 in the extracted types. If Professor Punnett prefers to employ the term 

 " genetic factors " I am quite willing to use that phraseology. Punnett 



I Vol. IX, p. 303. 



