4 
Results of Crossing Grey {House) Mice with Albinos 
a mouse intermediate in colour between a black and a grey, and would therefore 
be denoted by B-0. 
Each of these colours occurred both uniform and marked with white. The 
white marking, as Cuenot observes, is subject to continuous variation. The parts 
fii'st affected are the tail and the paws ; then a small white mark may be found on 
the belly and on the top of the head. The white mark on the belly may grow 
forwai'ds and backwards, so as to cover the whole ventral surface ; laterally it sends 
out arms of whiteness immediately in front of the hind legs, these grow dorsal- 
wards and may meet and form a complete white belt. The mark in the head 
spreads forwards till it forms a good white blaze on the forehead, or further still 
till the front of the muzzle is completely white, and eventually it becomes 
continuous with the ventral white mark. 
The letter P in conjunction with the symbol for a colour means that the mouse 
is piebald and of this colour ; no attempt is made to indicate the degree to which 
the white marking has spread, though of course a record of this has been kept. 
Results. 
106 white mice were mated with grey mice and of these crosses 74 proved 
fertile. 
70 families contained only grey mice. Of the remaining four 2 contained 
mice of varying shades of yellow in addition to grey, and the original chinchillas 
appeared in the other two. Thus the first generation of hybrids consisted of 
342 mice, of which 329 were grey, seven yellow, and six chinchilla. 
The appearance of yellow in this generation is easily understood, if we assume, 
in the absence of any definite information on the subject, that the albino parents 
in each case were hybrids containing yellow and some other colour latent. Such 
mice would according to Cuenot's hypothesis produce some yellow and some grey 
when mated with pure grey mice, as yellow is dominant over grey and grey over 
any other colour which they might contain. 
Having no sort of evidence either as to the nature of the chinchilla coat, or as 
to its behaviour when pure and mated with other colours, it would be futile to 
indulge in speculation on the possible reasons for its occurrence here. 
The yellow mice when mated together produced yellow and grey and white. 
Thirteen young from four families were obtained, and of these five were grey, six 
yellow and two white. These numbers are of course too small for the proportions 
to have any significance, but the theoretical expectation for sixteen mice would be 
four albino, nine yellow and three grey. 
From the original seven yellow mice all the yellows and sooty yellows occurring 
in the experiments were produced. 
The original pairs are labelled A and B in the Appendix, the As, having the 
white and the Ba the $ . 
The offspring of the A and B crosses were mated with white mice and with one 
another. 
