A. D. Darbishire 
23 
transmission, dependent upon their ancestry, different from that of albinos whose 
ancestry contains no pink-eyed waltzers. 
Grandchildren of Hybrids. 
The children of hybrids consisted roughly of a quarter albinos, a half dark- 
eyed forms with coloured coats and a quarter pink-eyed mice with colour in the 
coat. The extracted albinos are unquestionably the recessives: the dark-eyed 
mice with coloured coats I have termed the extracted hybrids ; partly because 
they occur in the proportion of 50 and partly because they are asserted by 
Bateson and Castle to be what I have called them. The pink-eyed forms with 
colour in the coat which occur in the Mendelian proportion of a quarter I have 
called extracted dominants for similar reasons : I feel quite confident that Mendel 
himself would have sanctioned this classification, since the proportions agree 
closely with those which he obtained with his peas. 
The grandchildren of hybrids will be treated of under the following headings : 
(i) offspring of extracted recessives RR x RR, (ii) offspring of extracted hybrids 
DR X DR, (iii) offspring of extracted dominants DD x DD. 
(i) Offspring of Extracted Recessives. 
As could have been predicted with no fear of contradiction by those who are 
familiar with fancy mice the extracted albinos when paired together produce only 
albinos. For some I'eason I have been unable to breed from waltzing individuals 
of this category, and therefore the number of young which waltz is small, but it is 
far below that which would appear on Mendelian expectation, which is 1 in 12. 
For the albinos may be as regards waltzing either dominant or hybi'id, i.e. the 
kinds of pairs of albinos that can be made are three : 
(i) DD X DD. 
(ii) DD X DR. 
(iii) DRxDR. 
Of these pairs, (i) and (ii) should produce no waltzers, and (iii) should produce 
1 in 4. The whole number of young obtained was 94, and of these only two 
waltzed ! 
(ii) Offspring of Extracted Hybrids. 
I think that the most conclusive results which I have obtained are given by 
the results of pairing extracted hybrids : as the reader is aware, hybrids were 
paired with hybrids {DR x DR) and also crossed with albinos {DR x RR), 
the former giving offspring Avhich may plausibly be regarded as consisting of 
IDD + \ DR + l RR, the latter ^RR + ^ DR. So that, when pairing the children 
of hybrids to produce the generation which we are now considering, two kinds of 
extracted hybrids were available, (i) the result of DR x DR (which I will denote 
^ x^r= hybrid X hybrid) and (ii) the result of DR x RR (which I will call 
