SIKGLE-COMB MINORCA AND WHITE-CRESTED POLISH. 



15 



of classificatiou, is less essential tlian the fact of reappearance in about one- 

 fourth of the cases of the recessive characteristic. 



First hybrid generation crossed with Minorca. Since plain-head is R, the 

 cross is of the order DR X R : from which we should expect an equal number 

 of heterozygous (crested) and pure recessive (plain-headed) offspring. The 

 result, though based on small numbers, accords with expectation. 



Characteristic. 



All records. 



Hatched 

 chicks only 



Crest absent (RR). 

 Crest present (DR) 



Total 



5. Color of Top of Head. — First hybrid generation. All records give : 



Characteristic. 



Frequency. 



Wholly black . . . 

 Black and white. 



Total 



64.3 

 35-7 



.S6 



It is to be noted, first, that the white of the crest tends to disappear in the 

 later molts, some birds which showed it at 2 months losing it by 6 months, 

 or showing white at the tip only of the crest feathers. Further, with two 

 exceptions, all crests with white feathers belong to females (which have 

 larger crests than males). The two exceptional males are still young and 

 have only a trace of white remaining ; this will probably disappear in the 

 next molt. Third, the proportion of white to black in the crest is always 

 small — much smaller than in the Polish crest. Tue result looks like an 

 imperfect dominance of black. 



Second hybrid generation. Hatched chicks only give : 



Characteristic. 



Wholly black . . 

 Black and white 



Total , . 



Frequency. 



47.1 

 529 



I interpret this irregular result to be due to the imperfect dominance of 

 black. Twenty-five per cent of the individuals have wholly black gametes 

 and 25 per cent wholly black-and-white, or mosaic, gametes. The 50 per 

 cent with mixed gametes tend to be black, but contain white in varying pro- 

 portions. Something more than one-fourth of the black-and-white headed 

 individuals are males. 



