620 
Varietäten, Descendenz, Hybriden. 
C = Colour producer. 
G = Grey determiner. 
B =1 Black determiner. 
S — Self-pattern determiner. 
P — Piebald-pattern deter¬ 
miner. 
c = absence of colour producer. 
g = absence of grey determiner. 
b = absence of black determiner. 
s = absence of self-pattern determiner. 
p absence of piebald-pattern deter¬ 
miner. 
The colour producer is looked upon as a ferment, the grey 
and black determiners as chromogenous bodies which develope 
colour when acted upon by the ferment C. Grey and black are 
therefore only manifest when C is present in addition; any indivi¬ 
dual from which C is absent being an albino. In pigmented indivi- 
duals, black appers only when grey is absent. Similarly the piebald 
pattern only makes its appearance when the self-pattern determiner 
is absent (on p. 112 the author speaks of S as “dominant to P”, but 
in the scheme given above and on p. 116 they are not treated as 
allelomorphic to one another). 
The author’s results show that predictions based on the above 
scheme are verified experimentally in so far that unpredicted types 
have never occurred. In a few cases predicted types have not 
occurred, but the evidence is clear that it is due only to the smallness 
of the numbers at present obtained. 
With regard to the characters to which special attention has 
been paid, the author concludes that the completely self-black extracted 
forms are homozygous for black, and do not carry the albino 
character. Following Doncaster, the author recognizes two types 
of the “Irish” form, and amends Doncaster’s detinition ol the 
second of these two types. This last type (the “Irish b” type) is 
shown to be heterozygous in respect of S. Two zygotic forms ot this 
type have probably been recognized, namely, of the composition 
CcgBSsP, and CgBSsP respectively. The “Irish a” type has given 
no evidence that it carries the piebald character, and it is perhaps 
of the Constitution CcgBSP, in which case the piebald character 
would be masked by the presence of S in all the gametes. 
Of the various types of albino theoretieally possible, four have 
been shown to exist with certainty, and evidence indicating the 
existence of two other types has also been obtained. 
The conclusion, based on the results of breeding experiments 
in a large number of cases, that albinos may carry positive colour 
and pattern characters (although no colour can be developed owing 
to the absence of the complementary factor — C in the author’s 
scheme) has been ocularly demonstrated for the piebald “Irish” and 
seif patterns. Haacke described an albino rat in which the hair of 
the hood and back-stripe differed from the rest in texture, although 
quite without pjgment; and Doncaster, commenting upon this, 
suggests that such an animal would be found to bear the piebald 
character only. Mudge has found that, in the young albino rat, the 
pattern is rendered visible by some difference *in the texture and 
closeness of arrangement of the hairs, so that where in the pigmented 
animal there is colour, in the albino there is pinkness, due to the 
fact that the underlying skin shows through. The visibility ot the 
pattern is transitory; the author first noticed it in young which were 
about a month old, and it disappears when the individuals are 
about 2—months old. This case, as the author remarks, is ana- 
logous to that described by Lock in the “Maple” markings of peas. 
The interpretation placed upon the appearance of the coat in albinos 
