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



sheep; the females show an entire absence of horn growth and 

 the males bear the usual simplex condition of horns. 



A peculiar feature of the simplex horn, it will be remarked by 

 examining data in the different tables, in the offspring arising 

 from Merino crosses comprehends a striking irregularity in size 

 betwixt the right and left horns of many individuals. I under- 

 stand from trustworthy information that this lack of simi- 

 larity also exists to some extent in pure-bred Merino strains. I 

 regret that I have no precise data to offer upon this, since I 

 have been unable to get measurements of a large number of 

 Merino horns. All simplex horns are more or less subject to 

 variation; but of those derived from the Dorset Horn it is by no 

 means so apparent. This erratic variation, which does not occur 

 in the duplex horn of the Dorset, is, perhaps, due to the low 

 potency of the Merino horn determiner; or, in other words, the 

 impetus to somatic growth from the determiner is not always 

 sufficiently great to repel completely some local agency, as, for 

 instance, unequal thickness of skin over the budding horns, 

 counteracting development. Neither horn possesses an advan- 

 tage in size ; an average of all cases at this Station shows approxi- 

 mately an even division. 



Little comment need be made on the matings of Dorset Horns, 

 (Sec Table V). There may be a heritable tendency anent size 

 of horn, but, owing to limited data, no inferences can be drawn 

 at present. However, I am making measurements this year of 

 the horns of about two hundred Dorsets of both sexes, composing 

 a flock in Vermont. Several sires have been used, and knowing 

 the sizes of the horns of both parents and offspring, I may be 

 able to recognize a mode of inheritance. 



Only a few representative examples have been shown of mat- 

 ings of hornless breeds. (See Tables VI and X). Altogether 

 113 individuals have been used in these crosses, being carried along 

 to study characters other than horns. Where a Native * has 

 •entered a cross, the F 2 generation is given to show that these 

 sheep belong to pure hornless strains. In fact, our Native ewes 

 were selected with care and all were given breeding tests before 

 being introduced into the experiment. 



More offspring from the Southdown-Dorset crosses (See 

 Table VII) were expected. The fertility of our first Southdown 

 ram used proved most uncertain, only one lamb being born from 

 him. It, moreover, was stillborn and deformed, and a descrip- 

 tion of it, consequently, could not be included satisfactorily in 

 the data. The wide variation of the simplex horns in the different 

 males is worthy of notice. Apparently the horn determiners and 

 inhibitors do not always exist in equal degrees of strength. The 



* Native is the term applied to the ordinary grade sheep which exist all too prevalently in New Hampshire, 

 their oritrin bein< most difficult to trace. 



