112 Experimental Zoology 
Type 3 might give types 3.4 5 
Type 4 might give types 4 
Type 5 might give types 4.5 
Type 6 might give types 45 6 7 
Type 7 might give types 4 6 7 
Thus the wild type 1 is dominant to all the others, z.e. its 
offspring may belong to any one of the other types which must 
have been recessive in its germ-cells. The gray forms 1, 2, 3, 
are also dominant, in the same sense, to the black forms. The 
albinos give albinos only. “It appears that types 3 and 5 could 
be ultimately bred true. As to 6 and 7, the evidence is not very 
clear; but as I understand the account, neither was completely 
freed from throwing the other. The breeding in these types 
was the least successful and extensive. Possibly they are illus- 
trations of the Mittel-rassen of de Vries. It is especially 
noteworthy that the gray-and-white type 3 and the black-and- 
white type 5 do not give rise to self-gray gametes or to self- 
black gametes, a fact found again in mice. We see, therefore, 
that there are gametes for black-and-white and for gray-and- 
white, each of which may behave as a single character and domi- 
nate over albino.” * 
When pure black-and-white rats were crossed with the wild 
gray rats, all the colored types might appear in generation (F,) 
except albinos. In other words, the black-and-white do not 
separate, they are not resolved in the germ-cells, as other experi- 
ments also indicate. Crampe found further that black-and- 
white individuals that gave albinos in the first generation when 
bred inter se also gave albinos when bred to albinos. In this 
case the black-and-white individuals had probably arisen from a 
cross between black-and-white and albino, so that the albino 
(and not the white of the black-and-white) gave the white mice 
just mentioned. On the other hand, Crampe found that when 
the black-and-white rats did not themselves throw albinos, they 
did not do so in the first generation when bred to albinos. 
1 Bateson, Proc. Zodl. Soc. 
