SIZE INHERITANCE IN DUCKS 31 
the birds had practically gained their adult size by October 22. 
The mean weights of the three lots is as follows. 
SEX OCTOBER 13 | OCTOBER 22 NOVEMBER 10 
Malestente chee ok. 1039 1076 | 1089 
Remlalesseescen entero. 935 937 | 967 
This stock of mallards is the pure semi-domestic Anas boschas 
used in the English game preserves. They are perhaps slightly 
larger than pure wild mallards, which average about 1000 grams 
for the males, depending somewhat on food supply; (no large 
series of the weights of wild mallards is at hand). 
MATINGS 
In the spring of 1910 three female mallards taken at random 
from the original stock were mated. with one of the Rouen stock 
males. At the same time two female Rouens were mated with 
a male mallard, but the two settings of eggs which were obtained 
from this last mating proved tobeentirely sterile, due undoubtedly 
to the small size of the male bird. While on the subject of this 
attempted reciprocal cross, it might be well to state that there is 
probably little or no error introduced into the experiment on ac- 
count of a difference in size of the eggs in the two races. The 
lengths of seven Rouen and seventeen mallard eggs were measured 
in 1909. There is a good deal of variation in the eggs of both 
strains and an overlapping of the two variation curves. The 
Rouen eggs are roughly 2.40 inches in length and the mallard eggs 
2.25 inches in length. 
The F, eggs from the mating male Rouen xX female mallard 
were set in two lots and hatched on the same date, May 29. They 
were reared under hens in exactly the same place and under the 
same conditions as the two parent classes. Both this group and 
the F, birds were banded. ‘These F, birds, ten males and three 
females, were weighed October 29, at the age of five months. 
The class is obviously too small, but as far as it goes it shows a 
remarkable uniformity. Between the largest and smallest males 
