70Exhibit M 2—3
M 3All the rabbits are homozj'gous for th2 black factor B.
Homozygous agouti = AA BB EE.
Black rabbits may be either :—
(1) Rabbits of the constitution aa BB EE. These breed true and
behave as simple recessive to agouti.
(2) Rabbits of the constitution AA BB EE I')D., i.e., agoutis to which
a double dose of D has been added are pure blacks in appearance,
when only a single dose of D is added the animal shows some
agouti markings and is an agouti-black. Such rabbits have always
proved to be heterozygous, and when mated together give blacks,
agouti-blacks, and agoutis in the ratio 7:6:3.
(3) Rabbits of the constitution AA BB Ee Dd. An agouti-black
(AA BB EE Dd) becomes a pure black when heterozygous for E.
Such blacks when mated with blacks of constitution aa BB EE dd
throw some agoutis and also some agouti-blacks.
Further, the experiments have shewn that the factor D is coupled
with E in the gametogenesis of rabbits of the constitution AA BB Ee Dd.
The gametes produced by such animals are of two kinds only viz—
ABED and A B e d. When mated with a tortoise aa BB ee dd they
give blacks and yellows only—and no agoutis. So far as is known, the
coupling between E and D is complete. At present this is the only
case of coupling between characters yet worked out in a mammal.
Experiments with Poultry, illustrating the recombination of
characters.Brown Leghorn $
(a) Coloured (chiefly brown)
plumage
{&) Normal feathersor (a) White plumage (with
without slight buff tinge)
(/>) Silky feathers
(n) Coloured
(à) Normal feathers
F2 Generation
Coloured plumage Coloured plumage White plumage White plumage
Normal feathers Silky feathers Normal feathers Silky feathers
