May, 1912.] INHERITANCE OF HORNS IN SHEEP. 21 



breeding time. Consequently, our offspring from matings of 

 Merino rain with hornless breeds (See Table VIII) are few in 

 number, and do not permit of extensive comparisons. I had 

 hoped from this cross to find some F 2 females having knobs. 

 However, this feature has been clearly shown in the female F 2 

 offspring from matings of hornless breeds with Merinos (See 

 Tables XII and XV), where six females bear the knob character. 



In the F 2 individuals obtained from Merino crosses with horn- 

 less sheep (See Tables XII and XV) a reappearance of long horns 

 in the rams occurs, although the ratios of these horns are some- 

 what less than the average for the horns of Dorsets. The ewes 

 either bear knobs, scabs, or are hornless. The striking dissimi- 

 larity between the lengths of the right and left horns of Merinos, 

 especially simplex, is also shown. This variation is sometimes 

 very slight and cannot be distinguished without actual measure- 

 ment. Since we have used a tape marked in millimeters, we have 

 been able to discover fine differences. 



Matings of Dorset Horns with Merinos (See Tables IX and 

 XVI) add corroboration to my former statement that the knob 

 of the Merino female is represented in the germ plasm by the 

 double determiner. If only one horn allelomorph were present, 

 we should expect some shorthorned male offspring. The horns 

 of the Fi rams are all sufficiently large to permit them being in- 

 cluded satisfactorily in the long horn category. The ratios, it 

 is true, are less than those of the horns of Dorsets. However, 

 this can be explained by reason of the fact that the horn deter- 

 miner (H') of the Merino is less potent than that of the Dorset. 

 The females, 143, 145 and 162, (See Table IX), likewise bear 

 long horns. Some doubt exists, perhaps, as to the nature of the 

 horn of 162. The horn curved forward in a curious fashion, and, 

 had it not been sawed off, would have pierced the head below the 

 eye. Consequently, its length is not as great as it normally would 

 be. The circumference, however, is a direct indication that 

 it is a long horn, being even greater in that regard than 143, 

 which plainly bears a long horn. 



The 1912 F 2 generation (See Table XVI) adds further evidence 

 in support of these facts. A word or two more is necessary to 

 explain the gametic condition of D x Mo ram, 167, (Table IX 

 and XVI). His mother, 31, is most probably simplex horned, 

 and since his horn is comparatively short in relation to the 

 horns of 161, 163 and 164, the belief that it also is simplex is 

 strongly sustained. Consequently, it must bear the long horn . 

 determiner (H), since the gametes produced by his Jather_are- J^ 

 XHI and XHi and by his mother XH'I and X$QT In some 

 instances hornless Merino ewes have been indicated as possess- 

 ing a simplex horn. In all cases of this nature I am assured that 

 such is the condition, for I have based my assumption on the 



