24 Result of Crossing Japanese Waltzing with Albino Mice 
H X A). With these two kinds of extracted hybrids three kinds of crosses can 
be made : 
1. {HxH)x{HxH). 
2. (HxH)x{HxA). 
8. {HxA)x{HxA). 
Now ill Mendelian language these kinds of pairs are all DR x DR, for the DR 
produced by DR x RR is not different from the DR produced by DR x DR. And 
the similarity of these formulae is characteristic of the Mendelian conception of 
the reproductive organs of the hybrids. 
For it is well known that according to this view the hybrid contains equal 
numbers of germ-cells which produce the dominant character, and of those which 
produce the recessive ; and this is said to be true of the hybrids however far the 
individual is removed from the original cross, whether it is the result of the cross 
(i.e. the hybrid) or the great-great-grandchild of this. This is the ground on 
which the doctrine of the purity of the germ-cells and the law of ancestral 
heredity flatly contradict one another; the former asserting that DR x DR will 
produce 25 7o DD, 50 7o J^R and 2.5 7o for a very great if not an infinite 
number of generations ; the latter maintaining that the further the individual hybrid 
under consideration happens to be removed from the cross the less albinos will it 
produce : and that two hybrids whose mothers were albinos will produce more 
albinos than would two hybrids who have no albinos in their pedigree later than 
their great-great-great-grandmother. This seems to me to afford a case in which 
experiment could provide a decisive answer. I have made an experiment of this 
kind : that is, I have tried to see if by pairing together hybrids with different 
amounts of albino ancestiy I coiild obtain different percentages of albino individuals 
among the offspring. I have not had time to do this by producing successive 
generations of hybrids and counting the number of albinos in each : but I have 
done it by observing the difference between the results of making crosses of form 
(H X H) X {H K H), {H X H) x {H x A) and {H x A) x {H x A). 
'J'he ancesti-y of these kinds of pairs is perhaps brought more vividly before 
the reader's mind by considei'ing the following pedigrees : 
(i) WxA W^A WxA WxA 
{HxH)x{ffxB) H H H H 
Offspring of first kind, 
(ii) WxA WxA WxA Ax A 
{HxH)x{HxA) H H HA 
Offspring of second kind. 
