104 Mr. G. P. Mudge. On the Hereditary [May 8, 
We may, therefore, conclude that the “ Irish” } form in these experiments 
may have the gametic composition which I have assumed for it, z.c., CegBSsP. 
ba b6 7 
Fig. 1.-—Curve showing the ie ec oo corr eee, between prediction and actual result 
in a cross of “Irish” 6 x “Irish” 6. The line indicating prediction is the continuous 
one, that showing result is the broken one. The abscissee represent the different 
types of rats, and the ordinates the proportions in which they occur. 
(b) Piebald Parentage—In experiments 54 and 55 the “ Irish” 5 parents 
used were derived from a cross of Cr 6 6x Cr 5 (carrying albinism recessive). 
The Cr 66 grandparent was in both experiments derived from a cross of 
black variety of wild grey x Cr 4 (see experiments 47, 57, and 59). From 
such a cross of Cr 66xCr 5, there are expected among the offspring, in 
addition to the Cr 4 and Cr 5 types, two forms of “ Irish” 0, v.e., CgBSsP and 
CegBSsP. 
If we suppose that in both of the experiments (54 and 55) one of the 
“Trish” b parents was a CgBSsP and the other a CcegBSsP, then the 
predicted results will differ from that where both are CcegbBSsP in the 
absence of albinoes. The expectation is :— 
2 Cr5+1 Cr6a+4 Cr 6 641 Cr 7. 
The actual result of the two experiments combined is :-— 
3 Cr 5+8 Cr 6 b+1 Cr 7. 
The special feature of the prediction, 7.¢., absence of albinoes, is thus far 
confirmed. Considering the smallness of the number, the approximation to 
prediction, with regard to proportion of the different types, is sufficiently 
close to be significant. .The proportion of Cr 5 is exact, that of the 
Cr 7 is as near as it can be with the number of individuals present, while 
that of the Cr 6 61s two too many. The predicted Cr 6 a is absent. 
In connection with the missing type, the remark made on pp. 99 and 106 
should be borne in mind. Expected types do not always appear in the first 
litter, and some not until the third litter, even though the early litters may 
be of large numbers (eight or more). 
