73 Mr. G. P. Mudge. On the Hereditary [ May 8, 
were those of Crampe (13 and 14), published in 1877, 1883, 1884, and 1885. 
All his papers were therefore published antecedent to the re-discovery of 
Mendel’s Principles, by De Vries, in 1900, and the results were not stated in 
a form which render it possible to determine certainly whether they are in 
accordance with Mendelian expectations or not. Crampe’s experiments were 
analysed by Bateson in 1903(5), and he showed that a few Mendelian 
conclusions could be deduced from them. 
But at about the same time that I commenced my experiments, 
Doneaster had also instituted a similar series with the same kind of animals, 
and in 1908 he published his results (15). 
He also discussed Crampe’s experiments, and as the outcome of his own 
work he reached the following conclusions :—(1) That albinoes may carry 
the determiners for grey and for black, or for both. That some may carry 
the piebald determiners, and others the self pattern determiners. (2) That. 
Crampe’s “Irish” form consisted of two sub-forms, which Doncaster 
designated “a” and “0.” (3) That the “ Irish” “a” and the wholly black 
form Cr 7, contained no piebald. (4) That, tentatively, the Cr’7 (wholly black) 
form may be regarded as an extreme form of the Cr 6 a, and is not a separate 
variety. (5) That with regard to pattern there are only two allelomorphs in 
rats, ae, “self” and “piebald,’ and that when they are crossed together, 
dominance is not complete. (6) That the “Irish” 6 form is a heterozygote 
produced by crossing black (Cr 7) or “ Irish” a with black and white. (7) That 
the proportions of types which appear in successive litters may be diverse. 
With regard to these conclusions, my work confirms them all, with the 
exception of No. 4, and it adds further evidence in support of most of them. 
In addition, some new results are reached. With respect to these latter and 
to the extended evidence, see “ Summary of Results,” p. 115. 
I have to express my thanks to Mrs. Gunn (Miss Gertrude Smith), who for 
three years daily superintended the feeding of the rats. To her conscientious 
care must be ascribed much of the success of the breeding. 
My thanks are also due to Mrs. F. Judkins, of Sark, who personally took 
‘considerable trouble to obtain for me three pairs of the old English black rat. 
(Mus ratius). Unfortunately, this species apparently will not breed with the 
grey rat (Mus decwmanus), nor with any of the tame types. I have kept. 
M. rattus mated with all the varieties for considerable periods, but without. 
result. 
To Mr. Reginald I. Pocock, I am also indebted for two specimens of the 
black variety of the wild grey rat, which were trapped in the Zoological 
Gardens, and for five young specimens of J. rattus, which were born there, 
from a pair presented by Mrs. Judkins. 
