E. H. J. Schuster 
5 
In the former case the crosses produced are labelled C and D, C having the J' 
a product of an A or B cross and the $ an albino, and D being the reciprocal 
of this. 
The Cs produced 282 young of which 130 were albino and 152 coloured, the 
Ds produced 255 young of which 131 were albino and 124 coloured. Thus 
together we have 537 young of which 261 are albinos and 276 coloured. Con- 
sidering merely the characters, colour productiveness and albinism, the Mendelian 
expectation would be 268"5 of each, so that the actual result obtained is in fairly 
close agreement with it. 
If we go on to an enumeration of the actual colours obtained, we find among 
the Cs 25 black, 102 grey, 2 intermediate between grey and chinchilla, 2 golden 
agouti, 16 grey marked with white, and 7 black marked with white. 
Among the -Ds we have 26 black, 77 grey, 1 golden agouti, 1 yellow, 1 sooty 
yellow, 1 chocolate, 12 grey marked with white and 7 black marked with white. 
Speculation as to the proportion of the various colours seems to be useless, but 
if one assumes that some of the albinos employed both in the A and B and in the 
C and I) crosses had any other characters but uniformity and greyness latent in 
them, then one would expect that these characters would become apparent in the 
coats of some of the mice produced. 
This remark applies with equal force to the consideration of the results of the 
various other crosses described below, but it will not be repeated again. 
The offspring of the A and B crosses were paired together and these pairs are 
labelled E. The .fi's produced 119 albinos, 27 blacks, 17 intermediate between 
black and grey, 201 greys, 9 intermediate between chinchilla and grey, 9 chinchilla, 
8 golden agouti, 9 yellow, 3 sooty yellow, 1 chocolate, 19 grey marked with white, 
3 black marked with white, 1 chocolate marked with white, and 1 chinchilla 
marked with white. That is to say 119 albinos and 308 coloured. 119 is at any 
rate a possible approximation to the Mendelian quarter. The 308 coloured mice 
should be composed of ^ pure colour producers and | hybrids between albinos and 
colour producers. 
The F and G crosses were made to test the truth of this. The Fs have 
coloured offspring of the Es for $s and albinos for (/'s. The Gs are reciprocal. 
Out of 87 of these crosses 32 produced no albino young and 55 produced some 
albino young. 32 is a fair approximation to i of 87. 
The colours of the young contained in these 32 families is as follows : 18 black, 
1 intermediate between black and grey, 95 grey, 2 intermediate between chinchilla 
and grey, 1 yellow, 8 sooty yellow, 1 golden agouti, 6 chocolate, 20 grey marked 
with white, 13 black marked with white. 
The 55 families produced 141 albinos and 137 coloured mice. If these are to 
be regarded as hybrids equal numbers of each should be expected ; and a fair 
degree of equality is obtained. If we add these numbers to the results of the C and J) 
crosses with which they are to be associated, we get out of 815 mice 402 albino and 
413 coloured. 
