- RECENT ADVANCES IN ANIMAL BREEDING, 131 
Now let us look at the posterity of the three kinds of mice denoted by 
the formule OO, OC, and CC. OOs, i.e. albinos, when mated together 
produce only albinos ; OCs also when paired breed true with very rare 
exceptions ; while the offspring of CC x CC fall as before into the three 
categories OO, OC, and CC in proportions which I have not yet 
determined. 
The inheritance of colour in this case is shown at a glance in the 
following table :— 
OO OC* 
Ye ee 
00 cc oC 
8 AG, ER CER 
BS ms 
OOs (OD CC.. OC OC 
_ Now let us consider the generation, produced by mating the hybrids, 
from the point of view of its progression. Less than a quarter of. them 
waltz. But the deficiency is probably due to the fact that waltzers are 
constitutionally weak creatures and are more likely to die before they 
reach the age at which their characters can be recorded than other mice 
are. What is of interest is that the waltzing habit is not necessarily 
associated with that colour character OC with which it is associated in 
the pure strain, but is distributed at random over the three categories, 
OO, OC, and CC. 
We have so far confined ourselves to the description of phenomena. 
Now let us consider two theories which have been put forward to account 
for them; first, one by Von Guaita associated with the name of 
Weismann, and secondly, one by Bateson associated with the name of 
Mendel. 
The theory suggested by Von Guaita was intended to account for the 
results of a hybridisation experiment, similar to mine except for the fact 
that his waltzers had black eyes, carried out by himself. 
He suggested that there were two kinds of factors in a germ-cell that 
. gives rise to an albino; one, which we may call M, which determines that 
the organism which develops from the germ-cell shall be a mouse, and 
another, A, which makes that mouse an albino. And similarly in the 
case of the waltzer, its germ-cell contains an M similar to that of the 
albino, and a factor, W, which makes it what it is, a waltzer with pink 
eyes and fawn-and-white coat. Now M and M are supposed to be the 
same ; but A and W different and antagonistic. So that when an albino 
and a waltzer are mated it is a question which of the two factors which 
are antagonistic, W or A, will be manifested in the offspring. What 
* It may be objected that I have introduced an element of confusion by represent- 
ing one homozygote by two similar letters, the other by two different ones, and the 
heterozygote by two similar ones. But this objection is successfully met by saying 
that my formule can only lead to confusion among those students who have not been 
taught that such formule are nothing more than conceptual descriptions of features 
of the germ-cells which we haye not yet perceived. And such beginners will be con- 
fused anyhow. 
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