Íslenskar landbúnaðarrannsóknir - 01.03.1970, Side 19

COLOUR INHERITANCE IN ICELANDIC SHEEP 17
ed on each other. In the combined pattern
each of the basic patterns shows its effect
on inhibition of pigment independently of
the other pattern, so that the resulting
colour shows the sum of these two patterns
in pigment inhibition.
Ibis colour is extremely rare. The
author has only observed one animal of
this colour, and no previous account of
its presence is known. This animal, a one
year old ewe, showed the typical badger-
face-mouflon head pattern, but on the
whole the liead colour was lighter than in
black badgerface-mouflon due to the dilu-
tion from tlie grey mouflon pattern.
On the body, the grey mouflon pattern
had inhibited the formation of pigment in
the undercoat, so the upper part of the
body showed white colour. An exception
was the dark borderline around the white
belly, where the dark outercoat fibres still
remained black, cf. description of colour
no. 12. Except for these black outercoat
fibres on the borderline, the body produc-
ed white fibres only. The inside of the
legs of this animal was almost white, but
the outside similar to that of grey badger-
face.
The head pattern af tliis animal showed
quite clearly the dark bars between the
eyes, earlier belived to be the main char-
acteristic of the badgerface pattern. The
rest of the animal, however, showed no
signs af any patterns whatsoever, except
the dark colour on the feet and the black
fibres on the borderline between the side
and the belly.
Colour 17 — greybrown badgerface-
mouflon
This colour has never been observed,
but would be produced by replacing black
pigment with brown in the grey badger-
face-mouflon colour. From tlie available
evidence about the inheritance of tlie
colours it should be possible.
D. WHITE MARKINGS
IN NONWHITE SHEEP
The white markings often shown by non-
white sheep, are unpigmented areas on a
pigmented background. They can there-
fore only manifest themselves in sheep
showing pigment. It has further been
found in the Icelandic sheep that the
white markings are very rarely manifested
in sheep with tan pigment, so in the fol-
lowing the discussion will be confined to
white markings in nonwhite sheep with
either black or brown pigment present.
d’he distinction between white markings
and pattern is such that the pattern shows
a very high degree of symmetry, and
borderlines between pigmented and un-
pigmented areas are not clearly defined.
The pattern may also show a regular mix-
ture of pigmented and unpigmented fibres
within a given area.
White markings, on the other hand, are
very rarely completely symmetrical, al-
though some degree of symmetry is usually
found. Borderlines between white and pig-
mented areas are clearcut, at least at birth.
The birthcoat shows only wliite fibres in
the wliite areas, and the basic pattern in
the nonwhite areas is completely unaffect-
ed.
White markings can, as far as can be
seen, occur simultaneously with any of the
patterns.
In the classification of colours in the
present study, the main colour, i.e. the
basic pigment and pattern combination,
was therefore determined first, and then a
separate description was given of the white
markings, independently of the main co-
lour.
Because of the great variation and lack
of symmetry in the white markings, some-
what arbitrary, but fixed rules had to be
laid down for the classification of the
markings. Some overlapping of classifica-