1907.| Transmission of certain Coat Characters in Rats. 105 
We may, therefore, regard these two experiments as affording initial 
evidence that this particular type of “ Irish” 0, 2.¢., CgBSsP as contrasted to 
CeeBSsP has been actually produced. 
(2) “ Irish” b x Prebald Black-White = Cr 66x Cr 5 
Five matings of this nature have been made (experiments 56, 57, 58, 59, 
and 59a). In experiment 56 the Cr 5 parent was known by two previous 
testings to be homozygote. In experiments 57 and 59 the Cr 5 parent was 
known from previous testings to be carrying albinism recessive. In 
experiment 58 the Cr 5 parent was not tested, but since both its parents 
carried albinism recessive, the chances are equal that it also carried albinism. 
In experiment 59a the chances are also equal that the Cr 5 parent is either 
homozygous or carries albinism recessive. 
The “ Irish” } partners were in four experiments (56—59) members of the 
same parents, and were derived from a cross between a black variety of wild 
erey x Cr 4 (experiment 47). The albino parent was derived from albino 
grandparents purchased from ordinary dealers, and it was therefore, in all 
probability, carrying both black chromogen and piebald pattern determiners. 
The “Irish” 0 partners in these four experiments may be, therefore, 
represented by the symbol CegBSsP. The piebald parents in experiments 57, 
58, and 59 will be represented by the symbol CegBsP. 
The predicted offspring in such a cross will be :— 
2 Cr 4+3 Cr 5+53 Cr 6 0. 
We 4a =) 
Zale Or pigmented, (== 1 73) 
The actual result for experiments 57 and 59 combined is :-— 
i Cr ee Cr 5+20 Cr 6 642 pig. eyes.” 
12 alb. 34 pigmented. = 1: : 3 nearly. 
In these two experiments (57 and 59) where the actual gametic factors 
are known with some degree of certainty, the prediction of proportions of 
Cr 4 to the pigmented types and the actual result are practically identical. 
The proportion, however, of Cr 6 0 is a little too large. 
In the case of experiment 57 there were five litters, and since the details 
are significant, I append them :— 
* At birth the pigmented individuals can be immediately distinguished: from the 
albinoes by the pigmented eyes, which show through the skin. These two young ones 
died before their coat colour and pattern had developed. At birth the skin of- all sans is 
colourless and hairless. 
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