40 
GENETICS: CASTLE AND HADLEY 
self colored. This last class was found to be recessive and not to pro- 
duce English offspring, if mated inter se. 
The whiter-than-standard English proved to be homozygous for the 
pattern, the 'standard' English being heterozygous and breeding like 
their parents. 
From these observations it was clear (1) that the English pattern is 
a Mendelian dominant and (2) that the breeding of English rabbits 
resembles that of blue Andalusian fowls. For the standard bred animal 
is a heterozygote in the production of which there is bound to be a 
constant production of 'wasters' unless either the standard is changed 
or the homozygote can be changed to conform with the standard, pro- 
ducing an animal with more color. In the latter case homozygotes 
could be bred with each other and wasters eliminated. The question 
whether the pattern can be changed becomes therefore one of practical 
as well as theoretical interest. 
In making crosses of English with other breeds of rabbits, there was 
found to be considerable variation among the heterozygous English 
produced, some being much whiter than others; i.e., having less exten- 
sive colored spots. Plus (dark) and minu's (light) selections were made 
to see to what extent the pattern was capable of modification. These 
selection experiments are still in progress but will be reported upon 
at another time. 
The single-gamete experiment, with which this report will deal, was 
placed in the hands of P. B. Hadley, who has carried it out at the Rhode 
Island Agricultural Experiment Station. 
As foundation stock for the experiment a single heterozygous English 
rabbit of standard character (grade 2, fig. 5) was selected. To mate 
with him, it was desired to obtain a distinct breed of rabbits, free from 
the English pattern, and as pure (uniform) in all respects as possible. 
For this purpose the 'Belgian hare' was chosen. A buck and two 
does obtained from G. W. Felton, Cliftondale, Mass., were found to 
breed very true. From them was bred a stock of does very uniform 
in character, twelve of which, together with one of the parents (2A) 
were mated with the selected EngHsh buck which we may henceforth 
call by his record number d'21A. The young thus produced will be 
called 'Series I' offspring. About hah of them were self (non-English), 
the remainder (187 in number) were English.* The latter, although all 
* The total number of young obtained from 21 A, when mated with Belgian hare does 
has been to the time of writing 436. The English young now number 210, the non-English 
(self) number 226. For Series II matings presently to be described the corresponding num- 
bers of yoimg are: English 219, non-Enghsh 196, total 415. For Series I and II combined 
the numbers are : English 429, non-Enghsh 422, total 851. This is unmistakably a 1 ; 1 
Mendelian ratio. 
