C. J. Bond 89 



in 30 cases. In a later table (ibid, xxxiii) Barfurth tabulates 40 

 hyper-dactylous birds of which 8 were asymmetrical and of these 6 were 

 left-sided and 2 were right-sided. In a final list of 18 asymmetrical 

 birds 12 were left-sided and 6 right-sided. 



Barfurth also records in the same journal some observations on 

 extra rudimentary digits in the wing bones of chicks. Of 21 individuals 

 so characterised 2 were asymmetrical, the extra rudimentary digit in 

 both cases affected the right wing. In another group of 79 birds 6 

 asymmetrical cases occurred all with the extra digit on the left side. 



It is of interest to compare this asymmetry of toe development in 

 heterozygous fowls with other characters which under normal conditions 

 are symmetrically distributed. 



In Polydactylous Guinea Pigs there is a slight but definite tendency 

 for the supernumerary digit to appear on the left side, thus Castle {The 

 Origin of a Polydactylous Race of Guinea Pigs, Pub. Carnegie Instit., 

 May 1906) states that out of a total of 1219 individuals the extra toe 

 appeared on the left side in 630 and on the right side in 582. Attempts 

 to increase this asymmetry however failed. 



In an unpublished enquiry into the prevalence of Supernumerary 

 Nipples in Guinea Pigs, Mr Pechey of Leicester finds that out of 56 

 individual offspring of parents with supernumerary nipples 17 possessed 

 supernumerary nipples or teats. Of these 17, 10 were asymmetrical, 

 the extra nipple being placed on the left side in 7 cases and on the 

 right side in 3 cases. In 6 individuals with extra nipples on both sides 

 the larger and more fully developed teat was situated on the left side. 

 One individual (a female) had four extra nipples symmetrically placed. 

 These records show that a tendency exists for the supernumerary nipple 

 to appear on the left side in guinea pigs. 



Asymmetric Tail Feather Pattern in Pigeons. 



A blue-barred Homer cock with the normal number (12) of tail feathers 

 was mated with an inbred Fantail hen having 25 tail feathers. From 

 this Homer-Fantail cross 21 individual birds of the J^i generation gave 

 140 tail feathers on the left side and 140 on the right. 



In 50 F2 birds from the same cross there were 902 tail feathers, 456 

 on the left side and 446 on the right. 



Although the distribution of fully developed tail feathers in these 

 hybrid Fantail birds only shows a slight preponderance of numbers on 

 the left side in the F^ generation, further evidence of asymmetry is 



