1907.| Zransmission of certain Coat Characters in Rats. 113 
In both matings, the albino parent was obtained from an ordinary dealer ; 
ithat in experiment 47 from one dealer, and that in experiment 48 from 
another. It is important to note this fact. 
In experiment 47 there were 13 young in one litter, all of the “Irish” 0d 
type. 
In experiment 48, there were seven young, all at first of the “Irish” 6 
g; 
type, but one of these changed colour and became a Cr 2 in a few weeks after 
birth. This change of colour has several times occurred in my experiments 
and will form the subject of a separate paper. 
The further history of this Cr 2 member has been already considered, p. 108 
and experiment 66a. 
From the “ Irish” 6 individuals, the extracted self-black types to be con- 
‘sidered in the next cross were derived, as well as directly or indirectly, all 
the individuals of the “Irish” 6 crosses described in this paper. The details 
of the behaviour of these two types will, therefore, be found under their appro- 
priate headings. 
(b) HLxtracted Self-black x Albino —Four matings of this kind were made 
(experiments 43, 44, 45,46). Although there were four matings, only two 
black individuals were used, since the same individual ((1) 52/53) was crossed 
with three different albinoes. In experiments 43 and 44, this self-black 
individual was crossed with an albino which was derived from albino parents 
obtained from ordinary dealers. The zygotic composition of the albino may 
be, therefore, represented as coBsP. In each of these two matings there were 
eight young all “Irish” 8. 
Six of these from the second mating (experiment 44) were crossed inter se 
(experiments 51, 52, and 53). There is expected (supra, p. 103), on the 
assumption that their self-black parent is homozygote, albinoes and pigmented 
individuals in the proportion of 1:3 respectively. Actually it is as near as 
it can possibly be, ae, 4:11. 
The detailed expectation (Table I, p. 103), is :— 
4 Cr 4-3 Cr5+2 Cr 6 a@+6 Cr 6 6+1 Cr 7. 
There are produced :— 
aera 3 Cr >) +0 CrG ao Cr 6 0-2 Cr 7 
There is thus one Cr 7 too many and the expected “ Irish” @ is missing. 
But since some “Irish” a individuals have only a few white hairs on the 
chest, it is possible that they may be mistaken for Cr 7 until they are 
gametically tested. The result, therefore, may be regarded as confirming 
prediction in a very exact manner. 
