12 



INHBRITANCE IN POULTRY. 



On account of the difficulty of deciding iu the case of any young chicks 

 whether ' no-median and no-sphc comb ' is present, the last two classes are 

 combined in the right-hand column of this table and in columns a and/3 of the 

 table above. 



In comparing the fit of the expected percentages on the two hypotheses 

 with the actual, it is seen that hypothesis a is the better. However, the real 

 test will come in the F3 generation. On hypothesis a the single-combed 

 individuals bred together should produce only median-combed offspring. On 

 hypothesis ? they should produce some without median comb.* 



First generation hybrids crossed with Minorca. When the Y-shaped comb is 

 crossed back on the single comb of the Minorca (No. 26 c? ) the following 

 distribution of comb characters was obtained : 



Characteristic. 



Single comb 



Cleft comb 



Papillae or "absent 



Frequency. Per cent. 



21 



ti9 

 o 



52.5 



47-5 

 0.0 



This result accords well with the expectation that 50 per cent of the 

 combs shall be of the pure Minorca type and 50 per cent of the heterozy- 

 gous type. 



2. Nostrils. — First generation. No case occurred of a typical high nostril; 

 this characteristic is dominated by the narrow nostril ; but this dominance 

 is imperfect. In three cases (5 per cent) the nostril is recorded as one-half 

 high, /. e., having an aperture one-half as high as the extreme. In the 

 other cases, placed in class 2, the breadth w^as less, but still evidently influ- 

 enced by the germinal representative of the ' ' high ' ' characteristic. In two 

 skulls that were dissected the processus nasalis of the premaxillary bone 

 was present. 



class. 



Characteristic. 



Narrow 



a. One-third high 7 



b. One-half high 3 



High 



Total . 



Characteristic. 



Narrow 



a. One-third high 16 



b. One-half high 6 



High or nearly high.... 



Total 



Second generation. 



f. Per cent. 



45 

 22 

 18 



85 



529 

 25-9 

 21.2 



100. 



Second generation. In the second generation the high nostril appears again 

 in full or nearly full size in 21 per cent of the cases. Class 3 includes two 



*This topic is discussed again, generally, at page 68. 



t Including one thick comb with a median ridge in addition to the cleft comb, forming 



103. 



a typical pea comb. Seen in unhatched chick XVIII, 



