DDA4 MR. R. STAPLES-BROWNE ON [ Dee. 12, 
A discrepancy will be noticed between the numbers of birds 
illustrating the foot character and those which show presence or 
absence of “shell” in the same experiment. This is accounted 
for by the fact that it is possible to recognise the webbed or 
normal foot on hatching, or even in birds found dead in the egg- 
shell if sufficiently incubated, whereas the presence or absence of 
the “shell” can only be ascertained when the feathering of the 
young birds is fairly advanced. 
It was noticed that many of the young birds which were 
webbed were extremely weakly in the nest, and several of them 
died at a very early age. Of thethree extracted web-footed birds 
bred in Exp. 4 from “the DRx DR mating, not one was reared. 
The extracted webbed birds whose purity was tested were all 
bred from the DR x R matings. 
Discussion of Results. 
Foot character —It will be seen from the foregoing table that 
the feet of the F.1 generation, of which six birds were bred, 
were all normal, the web character behaving as a recessive. Two 
pairs of F.1 were mated, and in experiment 4 the webbed foot 
reappears in three birds out of the twelve, this being the exact 
proportion expected on the Mendelian hypothesis. 
From the other pair (Exp. No. 3), however, no recessives 
appeared, and the mating was repeated in 1904, as Exp. 6, with 
the same result. During the two years that these birds were mated 
together 29 eges were laid and 23 birds produced, all showing the 
normal foot character. The absence of webbed birds in this 
family was quite contrary to expectation, for 5 or 6 recessives 
were to be expected. In order to test the matter further, in 
1905 the two F.1 birds in question were mated to extracted 
recessives, and, as will be seen on referring to experiments 11 and 
12, webbed and normal offspring were then obtained in approxi- 
mately equal numbers in accordance with Mendelian expectations. 
The absence of recessives in the 23 birds in F.2. bred in 
experiments 3 and 6, is very remarkable. Whether it arose 
from any definite disturbing cause, or was merely a chance 
aberration, cannot be asserted. The behaviour of the same birds 
when mated to pure R clearly proves that their gametic production 
was then normal. 
In the matings of DR’s both with the original recessive web’ 
and with the extracted recessives eine results are simple. It will 
be noticed that in experiments 2,5, 11, and 12 fifteen webbed 
and fifteen normal birds were produced, the Mendelian expectation 
of such a mating being equality. 
It bemg imposeible to test the purity of webs bred by the 
DRx DR mmatines as the birds died in the nest, the extracted 
recessives from the DRx R matings were used, and experiments 
7, 8, 13, and 14 show the results. Nineteen birds were raised in 
these four experiments, all having the feet webbed. 
