20 N. H. AGR. EXPERIMENT STATION. [Bulletin 160 



inhibitor at times may so predominate over the single deter- 

 miner as to reduce somatic appearance of horn growth to a con- 

 siderable extent. In the offspring of the F 2 generation, however, 

 there is, with those possessing the double determiner, a complete 

 return to the long horned condition. Referring to Table XI, 

 F 2 ram, 269, is without doubt duplex horned, since length, 

 circumference and ratio correspond closely with those of the long- 

 horns of the Dorsets. The other F 2 horned males shown in this 

 table, from the condition of their horns, must be simplex. F 2 

 female, 229, is also long horned. It is not a little remarkable to 

 note that, with the exception of the Merino crosses, no extracted 

 females possess the slightest vestige of horn other than a perfect 

 long one, which goes to show how completely the single horn 

 determiner in held in abeyance by the double inhibitor. In 

 fact, the inheritance of long horns in sheep (Dorset Horn) is 

 very similar to that of colour blindness in the human family, 

 where the female will transmit the colour blind character to her 

 male offspring without being herself colour blind. For it re- 

 quires two "doses" of the colour blind determiner to produce this 

 disease in the female. In like fashion are horns in sheep trans- 

 mitted in heredity; the female will be either entirely destitute of 

 horns or possess a normal long horn according to the number of 

 horn determiners she holds in her germ plasm. 



The matings of hornless breeds with Merinos (See Table VIII), 

 so far as the Fi generation is involved, are of especial interest in 

 proving the assertion heretofore made that the knobs of Merino 

 ewes depend for their development upon two horn deter- 

 miners (H'H') in their germ plasm. Therefore, the knob or 

 scur represents the acme of complete horn production in the 

 Merino female. An examination of Table VIII shows that 

 every male offspring, derived from a cross between hornless 

 father and Merino mother with knobs or scablike growths, pro- 

 duced scurs or horns of a simplex nature. Now, were the mothers 

 simplex in regard to horns, some hornless Fi males would inev- 

 itably appear. The Fi females from the foregoing mating, of 

 course, were hornless but bearing one horn (H'h) determiner, as 

 subsequent matings to bring the F 2 generation prove. I strongly 

 suspect that most, if not all, of our hornless Merino ewes are 

 simplex in respect to horns, but, owing to the fact that most of 

 the ewes in this class bore females, we have not at the present 

 time any accurate means of ascertaining their condition in this 

 regard. Merino ewe, 45, however, we know must be simplex 

 since she produced a male offspring, 213, bearing scurs. 



Misfortune has attended our Merino rams for two years. 

 One died of derangement of the urinary organs during the mating 

 season, and another accidentally met his death. In both in- 

 stances it was found impossible to replace them opportunely at 



