1907.] Transmssion of certain Coat Characters in Rats. LL7 
8. That of the various theoretically possible types of albinoes, the following 
four have in these experiments been shown to exist, ze, cgBsP (102, 106,. 
110—111, and 112—113), cGgBsP (109, 112, 114), egBSsP (108, 112), and 
eGgBSsP (112, 114). To a lesser extent, the evidence indicates that two. 
other types, ze, cGBsP and cGBSsP, also exist (112). That is, of the four 
types experimentally recognised, so far, all carry both the black and piebald 
factors; one, and perhaps three, in addition, carry the grey factor, another 
the self-pattern factor, and one, or perhaps two, carry both the erey and self- 
pattern factors. The type cgBSP has not yet been demonstrated to exist. Of 
these four or six types, Doncaster has shown the existence of the two first: 
the others are new for rats. Hurst has shown the same thing for rabbits, 2.c., 
the existence of albinoes carrying B, and of those carrying BG. They also 
carry in some individuals the self character, in others the Dutch character, 
and in others both. The same thing has been shown for mice by Cuénot and 
Allen. There is thus a similarity in the carrying powers of albino rats, mice, 
and rabbits. In rats and rabbits it is to be noted no albino has yet been 
obtained which carries G alone, 2.¢., without B. 
9. That self-grey types (Cr 2) may carry both biack and piebald recessive. 
The following two forms have been experimentally recognised, 7.¢., CGgBSsP’ 
(111) and CcGgBSsP (111). One thus carries albinism recessive in addition 
to the black and piebald determiners, and the other does not. Clearly they 
correspond to the two races of “ Irish” 6 revealed in these experiments. 
From some of Doncaster’s experiments it can be seen that the Cr 2 type 
carries B and P recessive, but he made no attempt to ascertain whether 
different zygotic varieties of this type existed. The discrimination of these 
two zygotic varieties is therefore new. 
10. That piebald black-white types (Cr 5) may be homozygous for black 
and piebald, or may carry albinism recessive (105, 106). This conclusion 
can also be deduced from Crampe’s experiments; none of the Cr 5 types in 
Doncaster’s experiments appear to have been homozygous, and all carried 
albinism recessive. 
11. Externally considered, similar zygotes may have a different gametic 
constitution (see above, 6, 8,9, and 10). In experiments not yet published, 
it can be shown that self-grey forms not distinguishable in external features. 
from those in 9, do not carry g, and therefore B, though present as a reces- 
sive character, cannot appear. Zygotic characters alone are not, therefore, a 
safe basis for prediction. , 
This confirms and extends the same conclusion which has been arrived at. 
in all experiments which give Mendelian results. 
12. With regard to the number of allelomorphs for colour and pattern, the 
