The Editor: Concerning Prepotency 
others (and this whether the prepotency 
has been acquired through inbreeding 
or as a ‘sport’), or prepotent with one 
mate and not with another, or prepotent 
one year and not the next; because 
prepotency is of necessity subject to the 
influence of variation and reversion, and 
also doubtless of nutrition—more espe- 
cially of the germ-plasm prior to 
fertilization.” 
THE COMMERCIAL ELEMENT 
When a term has so many and so 
varied explanations, it might seem 
impossible to comprehend them all in 
any one definition. But if we view the 
question solely from the standpoint 
of the stock-breeder, I think we will 
find that these definitions really are 
summed up in one idea: To -him, 
prepotency is less a genetic than a 
commercial question: the prepotent sire 
is the one that produces a large propor- 
tion of offspring of high market value 
because of their possession in an 
eminent degree of the valuable commer- 
cial characters of the breed.” 
From a genetic point of view, un- 
fortunately, we can not reduce this 
complexity to simplicity, as we have 
done from the practical breeder’s point 
of view by assuming that it is, in the last 
analysis, merely a matter of dollars and 
cents. 
If we analyze “‘prepotency”’ from the 
standpoint of the geneticist, rather than 
that of the breeder, we find that it may 
appear in a number of ways, and that of 
two animals, one may be the more 
prepotent in one respect, the other in 
another. Its prepotency may be shown 
by 
1. Greater influence on the mean 
grade of the offspring. 
2. Greater uniformity in offspring. 
3. Greater influence (1 or 2) on second 
and later generations. 
4. Influence (1, 2, or 3) in greater 
variety of crosses. 
335 
5. Influence (1, 2, 3, or 4) in greater 
number of characters. 
Facing such a situation, I think ge- 
neticists might well avoid the use of the 
term ‘‘prepotency’’ and employ more 
definite words to express more circum- 
scribed ideas. But I do not think this 
need deprive live-stock breeders of the 
use of the term, as some geneticists 
would insist. After all, the word is the 
property of animal breeders, who use it 
to cover a fairly definite result, although 
a result that may be reached in various 
ways and capable of various explana- 
tions. 
My position in regard to prepotency, 
in short, is that it is a descriptive term 
belonging to practical breeders, not to 
geneticists. It is used by breeders in a 
way that they understand and find use- 
ful. The geneticist should not try to 
interfere with this use unless he can 
substitute something better; and at 
present I do not think he can. 
THE MENDELIAN EXPLANATION 
What he offers is, in general, the idea 
of dominance of Mendelian characters, 
to replace the idea of dominance (pre- 
potency) of an individual.” There is 
room for a good deal of discussion on this 
point, and I shall not take time here to 
discuss it. What the breeder wants is 
prepotent animals, and what he wants 
the geneticist to tell him, is how he shall 
proceed to get them. 
I mentioned, in the note on Brigham 
Young, three possible methods: (1) con- 
sanguineous marriage; (2) assortative 
mating; (3) chance. The _live-stock 
breeder might term these (1) inbreeding, 
(2) pure-breeding, (3) haphazard breed- 
ing or random mating. 
Of these, the first is considered by 
general recognition among intelligent 
students of breeding, to be the quick and 
effective way of securing prepotent 
animals. No student of pedigrees can 
doubt that inbreeding does result in 
prepotency. 
17 This suggestion was made by Dr. Sewall Wright of the Bureau of Animal Industry, at the 
conference mentioned by Mr. Rommel. 
To Dr. Wright I also owe the five-fold division of the 
subject from a genetic point of view, which is given a few paragraphs later. 
18 Hover, J. M. 
Finding the Prepotent Sire. 
April, 1916. 
JOURNAL OF HEREDITY, vii, No. 4, pp. 173-178, 
19 See e. g., Wentworth, E. N. Prepotency. JOURNAL OF HEREDITY, vi, No. 1, pp. 17—20, 
January, 1915. 
