VARIATION IN DOMESTIC ANIMALS 463 
out must’be struck from the records of observed mutations in domestic 
animals. 
Another case in sheep which has no importance, perhaps, from a 
practical standpoint is reported from Norway. Wriedt writes that 
among the old short-tailed sheep of certain districtsin Norway, individuals 
are found occasionally which possess very short ears. The short-ear 
character is dominant and alternative in expression when contrasted 
with the normal long-ear type. The records of one rather small flock 
descended from a single short-eared ewe showed that during 20 years 
not a single case of the production of short-eared offspring by long-eared 
parents was observed. The fact of thesimple character difference between 
long and short ears is clearly established by these records, but whether the 
short-ear type is the result of relatively frequent mutation may be a 
matter of some doubt. Ritzman in fact has pointed out that the short- 
ear character of native ewes when contrasted with the normal long-ear 
type of such breeds as the Rambouillet, Southdown, and Shropshire 
behaves as a simple character which exhibits alternative inheritance. 
This confirms Wriedt’s observation as to inheritance, but does not add 
any evidence as to the origin of the short-ear type. 
The most frequently cited evidence of mutation in domestic cattle 
is that of the polled character. Although this character is a simple 
dominant the evidence of mutation or segregation in particular cases is 
not always clear. Polled cattle have been known from ancient times and 
they have not been entirely wanting in the foundation stock of any 
modern breed. Within recent years the Polled Hereford and Polled 
Durham breeds have been established by utilization of polled mutants 
and by grading from horned Hereford and Shorthorn cattle respectively. 
Within these breeds the so-called double standard animals, 7.e., those 
which are eligible to registry in the corresponding horned breed herdbooks 
as well as in the polled records, presumably have all sprung from definite 
mutations. However, of nine polled sports listed by Spillman all except 
one were known to have near relatives that were polled. The two 
Hereford bulls Wilson 126,523 and Variation 152,699 both apparently 
came from horned ancestors. They were used by Boyd in establishing 
a pure race of polled Herefords. They were both heterozygous, for in 
matings with horned Herefords approximately half the offspring were 
polled and half horned. A herd of pure-bred polled Holstein-Friesian 
cattle has, also, been established in this country, but it appears to have 
been established by utilization of normal polled animals of which there 
are some representatives within the breed. Whatever the explanation 
as to the origin of these rather numerous polled sports, however, there is 
no question as to the correctness of Bateson’s suggestion that the polled 
condition is dependent upon a single dominant factor difference from 
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