106 PRINCIPLES AKD PKACTICE OF BREEDING. 



against a hereditary power which had been acquiring force for 

 ages.* His success therefore was the more marvelous. But 

 in merely giving a smaller head, etc., to his progeny, he did 

 not necessarily run counter to any special and fixed peculiarity 

 of breed.f The heads of Merino sheep vary in size. Some of 

 them are small. A malformation consisting of small ears, or 

 of the want of any ears, or of one or more imperfect legs, or 

 of having six legs, or any other deformity, does not impinge 

 the special characteristics of a breed, or of one breed more 

 than another. In all breeds alike, whether pure or impure, 

 there is a tendency in nature to preserve and restore the 

 normal form in the progeny ; but occasionally, as in the case 

 of Mr. Ely's sheep, that tendency is not strong enough to 

 resist the tendency of like to produce like. 



In all instances, pains should be taken to avoid breeding 

 between males and females possessing the same defect, and 

 particularly the same hereditary defect. In the first case, the 

 individual force of hereditary transmission in both parents 

 unites to reproduce the defect: in the second, both the 

 individual and family hereditary force unite to reproduce it, 

 and to escape from their combined efiects would, of itself, be 

 one of the strongest cases of " accidental " breeding. 



When the same individual or family defects are thus 

 transmitted by both parents to their ofispring, the latter are 

 apt to inherit them to a greater degree or extent than they 

 are possessed by either parent. Such an increase or aggrava- 

 tion may be regarded as inevitable where the common defect 

 is of the nature of an organic disease. If two human parents 

 are afiected by scrofula, and especially by hereditary scrofula, 

 in a slight degree, their progeny may be expected to exhibit 

 it in a much more malignant and destructive form. And the 

 same law, in transmitting diseases, or morbific conditions, 

 pertains equally to brutes. Relationship between parents 

 also exerts a strong influence in such cases, but this will be 

 more appropriately considered in the next Chapter. 



The relative influence of the sire and dam in transmitting 

 their own individual forms and other properties to the 

 progeny, has been the theme of much observation and 

 discussion. The prevalent opinion formerly was that each 



* But if he was a mongrel, lie brought the hereditary influence of Btraight-wooled 

 and probably pure blood ancestors to bear against that of his Merino ancestors, and by 

 breeding in-and-in, and by selection, he was made to give the preponderance to the 

 former in the particular under consideration. 



+ I have no definite or reliable information in regard to tlie form of head in the 

 Muuchamp Merino. 



