506 MR. R. STAPLES-BROWNE ON | Dee. 12, 
Variation in the Amount of Webbing. 
T have stated that the webbed foot is subject to considerable 
fluctuation, both when the character is observed to occur in 
normal strains and when it appears as an extracted recessive 
in these experiments. 
Table II. is arranged to show the approximate stretch of the 
web in the case of each bird recorded in the experiments. The 
observations were made by bending the foot and noting to which 
part of each digit the web was attached. In the table D 
stands for the digit, and ¢ for the phalanx. Unless otherwise 
stated, it should be understood that the web is attached to the 
distal end of the phalanx in question ; but if a fraction is inserted 
after the number of the phalanx, then the web is attached halfway 
or three-quarters of the way up that phalanx. No very accurate 
means of measurement were applicable, and the estimations 
should be taken as approximate only. 
The experiment numbers refer to Table I. 
Brackets are placed round the number of a bird to signify that 
the bird died either in the egg-shell or very soon after hatching. 
In all 37 web-footed Pigeons have been raised in the experi- 
ments, but upon such omally numbers discussion of the relationship 
of the several graduations is impossible. 
It may, however, be noted that some extremely small webs 
were raised in experiments 7 and 8, although the birds were bred 
from parents both showing the web character in a higher degree. 
Experiments 13 and 14 have already been discussed. 
Il. THe SHELL. 
It will be seen from Table J. that this character behaves as a 
simple recessive throughout the experiments with the webbed 
strain (but v. infra). 
In experiments 3, 4, and 6, out of the 29 birds bred, 6 show 
the “shell” in F. 2, a sufficiently close result. 
The extracted recessives bred true, as shown in Exp. 9. 
In Exp. 10 the number of recessives (5:2) is too high for a 
DRxR mating, which should have given equality, but the total 
is very small. 
Further Experiments with “ Shell.” 
The same Nun female which was used in the foregoing 
experiments was also mated to a Barb male. 
There is no need to give here a description of the Barb beyond 
the statement that the feathers on the head are always smooth 
aid no crest or ‘‘shell” is ever found. 
The results of the mating of Barb ¢ and Nun @ are recorded 
in Table IIT. 
