1907.] Transmission of certain Coat Characters in Rats. 111 
The two special features predicted are therefore present, 2.¢., absence of 
albinoes and presence of black forms. We may therefore regard this experi- 
ment as being initial evidence that a Cr 2 of the predicted composition 
CGgBSsP was produced. Of course, the experiment must be repeated, and 
larger numbers reared before it can be accepted as proved. 
But it is also predicted that an F 2 Cr 2 of composition CeGgBSsP will be 
formed. The offspring of such a member when it is crossed with an albino 
of cgBsP composition will differ from the one just considered only in the 
presence of albinces. In experiment 74, the second F 2 Cr 2 was crossed 
with an albino which had been extracted from a Cr 2, and may therefore have 
been carrying the grey determiner, as well as the black one. 
If the albino carried the black determiner only, the expected offspring is— 
A Ora Oro el Cro Cr. 5-- il Cr ibid: 
If it carried the grey determiner additionally, it will be :— 
S.Cr4-eo (rl aor ot! Cro--1 Cr é & 
The actual result is -— 
15 Cr4+1 Cr 2+1 Cr 3+4 pigmented eyes.* 
In the presence of albinoes, it satisfies one of the two special features 
of the prediction, though the absence of the black forms is disappointing, 
It is probable that the four individuals with pigmented eyes, which died quite 
early, included some black types. The presence of the albinoes is evidence 
that the Cr 2 contained albinism recessive. And such a type was predicted. 
Thus on the basis of the hypothesis of the nature of the Cr 2 of the 
F 1 generation (experiment 48), it is predicted that the Cr 7 type of the F 2 
generation (experiment 66a) shall be homozygous. And prediction in this case 
has been completely proved to be fulfilled. It is also predicted that among 
the Cr 2 members of the F 2 generation (experiment 66a), three types shall 
be produced (supra, p. 110), and of these, two have been shown to very pro- 
bably exist, by the nature of the F 3 generation (experiments 73 and 74). 
(5) Zygotie “ pattern” Albinoes. 
There remains one feature of importance to mention. [It is one almost 
new to science, and, as far as I know, has been observed only by Haacke (19), 
and then only in the case of a single individual. 
In experiment 74, just considered, where a particular Cr 2 was x Cr 4, 
there occurs in the F 3 offspring 15 albinoes. Of these, six were born in the 
second litter. Now, it is predicted that albinoes of such parents may include 
six zygotic types, 7.c.,ceBsP, egBSsP, cGBsP, cGgBsP, cGBSsP, and cGgBSsP. 
* These died before the coat colour or pattern had developed. 
