W. F. R. Wkldon 
45 
100 percentage; lOOs have a skin pigmented all over, but a strip of paler belly colour which, 
if white, would make the skin fall in the 80 to 95 percentage classes. This means that our 
100^ and IOO3/ ought to be Weldon's 6. As a rule our 100: are also his 6, but sometimes 
he denotes them by 5-6, and on some occasions he has called them 5. We have carefully 
considered these cases, but believe that our judgment, where not modified, must stand, as the 
belly .pigment in these cases is often almost as intense as the back — e.g. 55 as against 58 — and 
even when it is 9 against 19, this is not a pure white (1 only) but a shade of grey. We think 
our lOO.r for a pigmented belly with lighter hairs is more definite than terming the whole 
belly white, in which case our first number giving the extent of piebaldisra would have to be 
modified, but the measurement would be exceedingly difficult as the pigment is there and only 
gets more plentiful towards the back. As a rule Darbishire and Weldon judged the amount of 
pigment on the living mouse and the nature of the belly pigment was not so open to full 
observation as when determined from the skin. 
Weldon's colour classification was as follows : 
RoughlT/ Weldon's a=our 28 — 33; his b = o\n' 34 — 39; his c and d=onr 46 — 54; his e = our 
55 — 61 ; his /'=our 10 — 27 ; his ^ = our 40 — 42 ; his c/i = our 43 — 45. Naturally there is a good 
deal of personal equation in colour-determination, perhaps less with a colour scale than with 
mere verbal classification. Thus we should a priori have supposed c would range from about 
46 to 49 or 50 and d from 50 to even 55 or 56. But we find c used for as dark a tint as 55 
and d for as light a tint as 48. In the later records Weldon rarely, if ever, uses d, only c, 
so that its practical use is in the first or second hybrid generations, as in Mr Darbishire's 
paper. There d may be as low as 45, a tint we should call chinchilla. Our experience would 
make us doubt whether a rigid line can possibly be drawn between the various colour classes, 
with the possible but not certain exception of the yellows. Even here such judgments as b-c 
and b-f may. occur. The differences of d and c, and /' and g, may be so slight that intermediate 
classes may be formed as d-e, f-g. 
A w following the Weldon colour class in the brackets at the end of the description of the 
individual mouse marks that it was a waltzer. Intermediates in colour or in piebald class 
are marked by a hyphen, e.g. a-b or 3-4. 
Of the original stocks, the Japanese Waltzers were either bought or bred in the Laboratory. 
They were of pure stock, for they bred true to the parents when crossed only among themselves. 
There were very slight diftercTices of the fawn colour in the body, and all eyes were pink. 
A waltzer is distinguished by the letter W, and as a rule by its laboratory number. The 
a = yellow 
b = fawn-yellow 
c = pale wild colour 
(i=dark wild colour 
/" = pale blue grey ("lilac") 
g = chocolate 
c/; = chinchilla 
black 
