26 Result of Crossing Japanese Waltzing ivith Albino Mice 
It has already been pointed out that there is more than one kind of pink-eyed 
mouse with colour in the coat, and the difficulties which arise, when we attempt 
to derive these various kinds of mouse from the pure-breeding waltzer by any 
Mendelian process, have been indicated. 
So far as the observations go, they suggest (1) that a proportion of albinos, not 
yet determined, results from these unions ; (2) that lilac mice, paired together, 
breed true lo coat-colour ; (3) that dark-eyed mice are not produced in any large 
proportion ; (4) that the amount of whiteness in the coloured young is highly 
variable. 
(b) Extracted Dominants paired with Albinos. 
" Extracted dominants " have been paired with albinos in order to find out 
Avhether such unions behave according to Mendelian expectation. If the so-called 
extracted dominants were really of the constitution suggested by the name given 
to them, they should of course, when paired with albinos, produce a series of 
hybrids like those resulting from the original cross, albinos being absent. This 
was not found to occur. Out of 98 young produced, 12 were albinos — practically 
the same percentage as that given by one series of dark-eyed hybrids paired 
together — while one pink-eyed individual occurred. 
Most of the albinos used in making these crosses were "extracted" from the 
offspring of hybrids paired with albinos, as will be seen from the pedigrees given 
in Table G, p. 36 ; of the 98 young produced, 63 were from unions between such 
" extracted " albinos and the extracted dominants ; the seven unions between 
extracted dominants and albinos which did not include pink-eyed fa wu-and- white 
waltzers among their immediate ancestors produced 35 young, of which no less 
than 10, distributed among four of the unions, were albino ; of the three unions 
of this kind which produced no albinos, one was between a pure-bred albino and 
the same " dominant " individual which produced albinos when mated with another 
pure-bred albino ; there remains only two unions (Nos. 2H 79 and 2H 80) between 
pure albinos and " extracted dominants," which did not produce albino young ; as 
these two unions produced only 12 mice, their evidence is not conclusive. 
The experiments seem to show (1) that pink-eyed mice with colour in the coat 
are not always, if ever, " pure dominants," since they do at least generally produce 
some albinos when paired with albino mice of appropriate race ; (2) that the 
" extracted recessive " albino mice behave differently from albinos of other ancestry. 
The second result, together with other evidence already given, disproves the 
" pure recessive " nature of extracted albinos, the first makes it extremely doubtful 
whether " pure dominants " exist. 
Conclusions. 
The experiments described appear to justify the following statements: 
1. When the race of waltzing mice used is crossed with albino mice which do 
not waltz, the waltzing habit disappears in the resulting young, so that waltzing is 
