398 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
ancestor, the wild rock dove; in other words, reversions occur. Often, 
however, the results seem quite anomalous, which is probably due to 
the number of latent characters which different races of pigeons appear 
to carry. 
Mice.—Mendelian phenomena have been carefully studied in 
mice. Thus, when a grey mouse is paired with an albino, the hybrid 
offspring are always grey. When these are inbred, they yield greys 
and albinos, approximately in the proportion of 3:1. Thus Cuenot 
obtained 198 grey, and 72 albinos. 
Darbishire has obtained many results which harmonise well with 
Mendelian theory, while others require some ingenuity if they are to 
be fitted in with this interpretation. Asa good case we may cite one 
where the inbreeding of pigmented mice—derived from crossing pig- 
mented and albino individuals—yielded 159 pigmented young and 55 
albinos (53.5 being the theoretical anticipation). When similar 
hybrids were paired with pure albinos, they yielded 69 pigmented and 
69 albino forms, precisely as the theory would lead us to expect: 
D R 
4 
D(R) 
x 
a 
1 D+2 D(R)+1R 
x 
2R 
a 
DR) OR 
Cuénot crossed an albino AG (with latent grey) with an albino AB 
(with latent black), and obtained albinos (AGAB). He crossed a 
black mouse CB with an albino AY (with latent yellow), and obtained 
yellow mice (CBAY). He then paired AGAB (albino) with CBAY 
(yellow) and obtained 151 young—8r1 albinos, 34 yellow, 20 black, 16 
grey; the theoretical anticipation being —76 albinos, 38 yellow, 19 
black, 19 grey. This is an exceedingly striking and convincing case. 
Waltzing mice.—The mice of this interesting Japanese breed have 
among other peculiarities the habit of waltzing round in circles. When 
waltzing mice are crossed with normal mice, their abnormal quality 
behaves as a recessive. 
