12 



INHERITANCE OF CHABACTEEISTICS IN DOMESTIC FOWL. 



B. VARIABILITY OF THE Y COMB AND INHERITANCE OF THE VARIATIONS. 



As already stated, the proportions of the median and the lateral ele- 

 ments in the Y comb are very variable; the median element may, indeed, 

 constitute anywhere from 100 per cent to per cent of the entire comb. 

 Even full brothers and sisters show this variability. Thus the offspring of 

 No. 13 ? Single-comb Minorca and No. 3 <? Polish have the median element 

 of the Y comb ranging from per cent to 70 per cent of the whole comb. 

 Notwithstanding this variability of the median element in any family there 

 is a difference in the average and the range of variabiUty in families where 

 different races are employed. Thus the offspring of two Polish X Minorca 



ZAO 

 230 



10 20 30 40 50 60 70 80 90 



PERCENTILE GHADES OF MEDIAN ELEMENT IN THE Y COMB, 



FiQ A. — The frequency of the different forma of Y comb, each form being based on the 

 percentage of the median element of the Y comb to the entire length of comb. 



crosses show an average of 46 per cent of the median element in the comb; 

 the HoudanX Minorca cross gives combs with 60 per cent of the median 

 element; and in the combs of the offspring of two HoudanX White Leg- 

 horn crosses there is, on the average, 71 per cent of the median element. 

 The HoudanX Dark Brahma (pea comb) gives combs with an average of 

 87 per cent median element and the PoUshX Rose-comb Minorca cross 

 gives 89 per cent median. The rose-combed hens used in this last cross 

 were heterozygous, having single comb recessive; consequently they pro- 

 duced also chicks with typical Y combs. Such had, on the average, only 

 59 per cent of the median element and were thus in striking contrast with 

 the slightly split rose combs. In the case of the partially split rose combs 

 the median element ranged from 60 per cent to 100 per cent of the whole 

 length of the comb; but in the spht single combs the range is from to 100 



