INHERITANCE OF WOOL-CHARACTERS IN SHEEP                 377

a bimodal type of distribution of the figures for mean lengths in the long-wooled
breed (Border Leicester), with a more or less normal dispersion of frequencies in the
Cheviot. In the succeeding generations all parental types are found, but in the
F₁ a proportion of animals is encountered with a bimodal distribution similar to
the parental long-wool type. His conclusions support the findings of Davenport
and Ritzman, that wool-length and fineness are dependent in inheritance upon
multiple factors, rather than upon any simple Mendelian type of inheritance. His
results also tend to show that follicular activity is dominantly inherited in direct
ratio to the length of wool produced; this may be expressed by the statement
that long wool is incompletely dominant to short wool, the length depending upon
a multiple factor system.

In a series of observations carried out in this Institute, in crosses between ewes
of the Scottish Mountain Blackface breed, with rams of Derbyshire, Gritstone,
Cheviot, Border Leicester, Lincoln, Southdown, South African Merino, and Welsh
Mountain rams, we have found that the F₁ animals of both sexes, from the mating of
fine-wooled breeds (Merino and Southdown) to the Blackface, show very mixed
wool in which there is little uniformity in length or fineness, but in which the
character of fineness is generally intermediate between the parental types. Great
differences were shown between different F ₁ animals although the parental ewes
were themselves fairly uniform and of the same wool-type.*

In back-crosses to Merino ♂ the progeny showed a fleece of fine wool generally
approximating the Merino, but with a few coarse hairy fibres scattered through it,
whilst in the opposite back-cross the wool was similar to Black-face wool with a
greater admixture of fine wool-fibres and a much greater density.

In crosses by breeds carrying wool of intermediate fineness (Cheviot, Derby-
shire, Gritstone, and Welsh Mountain) the half-bred progeny showed greater
uniformity of wool-type amongst themselves but carried fleeces of mixed fibres.
Kemp, which is a common constituent of the Blackface fleece (average about 8 per
cent. by weight), was reduced to negligible proportions, and the fine-wool content
of the fleece was greatly increased. Back-crosses yielded animals in which the
wool was almost indistinguishable in fineness from that of the pure breed used.

In crosses from Lincoln and Border Leicester rams, strictly uniform classes of
F₁ animals were raised. The wool was coarser than in the other crosses and was
still mixed in type. We concluded from the series that inheritance of fineness
depended upon a multiple factor system and was of the intermediate variety.

* There are three distinct types of Blackface wool—the soft, open finer wool of the west of Scotland
generally; the hard, dense, coarse wool from south central and east-central Scotland, and the interme-
diate type from north-central areas. Between these there are all gradations.