A. D. Darbishirb 
5 
be superfluous : but in all cases of piebald mice I have made a drawing of the 
animal as seen from the right, left, and dorsal aspects by painting the colour- 
pattern on outline drawings of mice (printed for me by Messrs Palmer and 
Howe of Manchester) kept for the purpose ; and in cases of completely coloured 
mice with incompletely coloured tails I have merely drawn one view to show the 
arrangement of colour on the tail. All mice, which have reached the age at 
which they are sexed, have been described in this manner. 
Now suppose that one wants to pair these hybrids (First Crosses) together ; 
one proceeds in this way. 
Another mating book has to be used to enter the matings of the hybrids (to 
avoid hopeless confusion) ; and the numeral which indicates a cross or pair is 
preceded by some letter (such as H) to distinguish it from the same number 
which refers to a cross between a waltzing mouse and albino. I have called these 
pairs or crosses H^, etc. The individuals paired are entered thus in the 
mating book : 
H, 
? 
^ V' March 9. 
Against 7'""" in the illustrated catalogue book is written, so that one is 
enabled to refer from the ancestry of a mouse to its place in the room (for of 
course all pairs of the same kind, i.e. H's. for example, are kept together). When- 
ever 7*"' is mated again to form another pair or cross, the number of each succes- 
sive pair in which it is concerned is put after it, so that if one wants to find 7"'"' 
one looks at the last number against its name in the mating book. 
The value of the illustrated catalogue lies in the fixct that in many families 
the brothers and sisters are so unlike that when they are again looked up 
reference to the catalogue will convince one that one is dealing with the right 
mouse : of course they are identified by the number on their cage, so that their 
picture is not a necessary means of identification, but it is an additional safe- 
guard against error. 
Fig. 7 represents a sample page of the illustrated catalogue on a reduced scale. 
Fig. 7. 
