1907.] Transmission of certain Coat Characters in Rats. 107 
extracted ones. In 64 it was extracted from a mating of two “Irish” 6 
parents (experiment 50). In experiments 65 and 66 the two albinoes used 
were brothers, and were extracted from a cross between a Cr 2xCr 5 
(experiment 38). 
I will therefore deal with experiments 60, 61, 62, and 63 together, 
since all the four albino parents are probably of the same gametic 
constitution. 
The expectation 1s :— 
2 Cr 441 Cri+1 Cr6 6 = 1 alb.: 1 pigmented. 
The actual result of the four combined experiments is :-— 
14 Cr 447 Cr 5+3 Cr 6 6+6 pigmented eyes.* 
Ss : 
oe ae te 
14 alb. 16 pigmented. ee Uae gl aa 
Result and prediction are thus almost identical with regard to the pro- 
_ portion of albinoes and pigmented individuals; they are so with regard to the 
nature of the types predicted, and doubtless had the six individuals with 
pigmented eyes lived, there would have been a near approach to expectation of 
the Cr 6 b type. 
Lxpervments 65 and 66. 
As already stated, the albino parents in this cross were derived from a 
Cr 2 x Cr 5 (experiment 38). The Cr 2 was derived from wild grey x Cr 4 (of 
ordinary dealers) (experiment 20).+ The Cr 5 was derived from Cr 6 6x Cr 4 
(of ordinary dealers) (experiment 62). The Cr 6 0 from black variety 
greyxCr4 (of ordimary dealers) (experiment 48). (See Descendants’ 
Table, Charts II and IIT.) 
From an ancestry of this nature the albino parent used in 
experiments 65 and 66 may have one of four zygotic compositions, «., 
cgBsP, cgBSsP, cGgBsP, cGgBSsP. The “ Irish” 6 parents will be CegBSsP. 
If the albinoes are of the nature indicated by the last two symbols, and are 
carrying the grey determiner, then Cr 2 individuals are expected in the 
offspring. They are absent. Albinoes and the Cr 5 type are also expected 
in any case, but the Cr 4 is absent in experiment 65 and the Cr 5 in 
experiment 66. The numbers, however, are small, and it has been shown 
that expected types do not always appear in the first litter. The results of 
these two experiments do not coincide in their proportions with prediction, 
and they are being repeated on a larger scale. 
_* These died before coat colour had developed. 
+ This experiment will be described in a later paper. 
