112 Mr. G. P. Mudge. On the Hereditary [May 8, 
With regard to the positive pattern determinants which they carry, we may 
regard them as of two types, 2.e., those carrying only P, and those carrying both 
PandS. It should be noted that in pigmented individuals S is known to be 
dominant to P. 
Hitherto, we have had to rely upon breeding tests in order to ascertain 
what pattern determinants are carried by albinoes. But of the six albinoes 
in the second litter of this cross, one died early, while three of the remaining 
five had quite distinctly the pattern of the piebald rat. One had also the 
pattern of a Cr 2 or Cr 6 0 (these two patterns are the same, only the colour 
differs), and the remaining one had that of a self-coloured individual. 
I do not purpose going into details here as I shall publish a full account in 
‘another paper. It will be sufficient to say that the pattern is rendered visible 
by some difference in the texture and closeness of arrangement of the hairs, 
so that where in pigmented individuals there is colour, in albinoes there is 
pinkness, due to the fact that the underlying skin shows through; and where 
‘in pigmented individuals there is absence of pigment, in albinoes there is an 
opaque whiteness, the skin not showing at all. Thus, in the “self-pattern ” 
albino mentioned above, the whole surface of the body exhibited a pinkness. 
The visibility of the “pattern” early disappears, for I first noticed it in 
early August when the young were a month old, and it had disappeared in 
early October. In more recent cases I have noticed that it disappears when 
the individuals are about two to two and a-half months old. 
It is thus in the highest degree probable that some of the piebald marked 
albinoes were of the cgBsP, cGBsP, or of the cGgBsP type, that the Cr 2 or 
Cr 6 } pattern was of the cgBSsP or cGgBSsP type, while the self-pattern 
one may have been of the cGBSsP type.* 
If this conclusion is valid, then the prediction which forecasts that a 
homozygote black shall be formed, that certain Cr 2 types shall also be formed, 
and which also predicts that certain pattern bearing albinoes will be produced, 
has in all these cases been fulfilled. 
Haacke’s single case(18) was evidently a piebald-bearing albino. The 
other types are here described for the first time. Lock has described a some- 
what analogous case for the “maple” markings in peas (21). 
(6) Self-black x Albino = Cr 7 x Cr 4. 
(a) Black Variety of Wild Grey x Cr 4.—Two crosses of this kind were 
made (experiments 47 and 48). 
* While this paper was passing through the press, this conclusion has been tested by 
mating a “self-pattern” albino with a Cr 5. There were six young, all Cr6 6. Since 
self is dominant to piebald, the Cr 5 could not have carried the self-pattern determiner. 
This result is therefore conclusive proof that the albino did so. 
