130 REPORT OF THE CONFERENCE ON GENETICS. 
RECENT ADVANCES IN ANIMAL BREEDING AND THEIR 
BEARING ON OUR KNOWLEDGE OF HEREDITY. 
By A. D. Darsisuire, M.A., Royal College of Science, London. 
Curtous results are obtained by crossing albino with the so-called 
Japanese waltzing mice. It is perhaps not necessary to say that an 
albino mouse is one with an absolutely white coat and with pink eyes, the 
pink colour in them being due, not to a special pigment, but to the colour 
of the blood in the vessels at the back of the eye. 
The colour of the waltzing mice used in this experiment is best 
described by saying that were it not for a patch of fawn on the shoulders, 
and sometimes on the rump, they would be albinos. Their curious 
movements, inaccurately denoted by the term “ waltzing,” are not likely to 
be forgotten by those who haye seen them. The animals appear to have 
no control cf the movements of their heads, nor of the direction in which 
they themselves proceed ; and, when they are awake, they spend most of 
their time in twirling round and round, apparently mad, in a very small 
circle. 
When these two are mated the result is a mouse hardly distinguish- 
able from our common house mouse (when the albino parent is pure bred). 
The hybrid, therefore, has a grey-brown coat and coal-black eyes. 
We start with a pink-eyed mouse with a colourless coat (which we 
may denote for brevity’s sake by the formula OO)—the albino, and mate it 
with a mouse which is also pink-eyed, but has a partially-coloured coat 
(which we may call OC), and get as a result a black-eyed mouse, with a 
fully-coloured coat (which we may call CC). So much for the nature of 
the hybrids as far as colour is concerned. Now for their progression. 
The hybrids never waltz. This is true of the hundreds that I have 
raised. 
Let us now consider the result of mating these hybrids together. 
First with regard to colowr. The offspring produced by the union 
of these hybrids fall into the three categories OO, OC, and CC, in the 
proportions 25, 25, and 50 per cent. respectively. That is to say, im 
point of colowr, on the average one mouse in every four is like its 
albino grandparent; one in every four like its waltzing grandparent ; 
and two in every four like their parents the hybrids. It should be 
mentioned that all mice falling into the category OC, for example, are 
not exactly like the Japanese waltzer in colour. For example, the fawn 
colour may extend over the whole body; or, again, a new colour, lilac, 
may arise, associated with pink eyes, in this generation. So long as a 
mouse has pink eyes and some colour in its coat it is reckoned as 
belonging to the category OC. But the number of colours that can 
co-exist in a mouse with pink eyes is limited; for example, neither a 
dark grey nor a black mouse ever has pink eyes. 
