556 MR. R. STAPLES-BROWNE ON [Dec. 12, 



Variation in the Amount of Wehhing. 



I have stated that the webbed foot is subject to consideiable 

 fluctuation, both when the character is observed to occur in 

 noi'mal 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 halfwav 

 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 I'efer to Table I. 



Brackets are placed round the number of a bird to signif v that 

 the bii'd 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 small numbers discussion of the relationship 

 of the several gi'aduations is impossible. 



It may, however, be noted that some extremely small webs 

 were raised in experiments 7 and 8, although the birds were bi-ed 

 from parents both showing the web character in a highei- degree. 

 Experiments 13 and 14 have already been discussed. 



II. The Shell. 



It will be seen from Table I. that this chai-acter 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 bied true, as shown in Exp. 9. 



In Exp. 10 the number of recessives (5 : 2) is too high for a 

 DR X R mating, which should have given equality, but the total 

 is very small. 



Further Exjjeriments vnth " 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 

 and no crest or " shell " is ever found. 



The results of the mating of Barb J and Nun 9 are recorded 

 in Table III. 



