A PIGEON WITH FIVE TOES 
Asarule, extra toes are rare in birds, but a few breeds of domestic 
fowl have regularly five toes. 
These breeds probably 
originated in such a bird as the pigeon shown here, the hind 
toe being split. 
The split toe is inherited to some ex- 
tent, and long continued breeding and selection would 
doubtless result in the establishment of a five-toed breed of 
pigeons. Photograph from I. O’Neill Brenan, Brisbane, 
Queensland, Australia. (Fig. 16.) 
extra toe on one foot. If sufficient has been said, very rare save for the 
effort were made, probably a strain of 
five-toed pigeons, corresponding to the 
five-toed Dorking fowls, could be estab- 
lished on this basis. It would be many 
generations before all the birds had 
five toes, but if the five-toed individuals 
were regularly selected for breeding, it 
can hardly be doubted that this selection 
would eventually produce an effect. 
The relative constancy of the five-toed 
condition in Dorkings and Houdans, as 
compared with instability in guinea-pigs 
is probably due very largely to the fact 
that the domestic fowls have been 
stringently selected for five toes. 
The five-toed condition in birds is, as 
domestic fowl. Geneticists have made 
numerous crosses of the five-toed breeds 
_ with four-toed ones, in order to work out 
the inheritance of the trait, but they 
have not met with great success. Pro- 
fessor Castle holds that it is a Mendelian 
trait and that its irregular behavior goes 
to prove that Mendelian characters are 
variable; but most geneticists do not 
admit that Mendelian characters are 
variable in this way, and are therefore 
confronted with considerable difficulty 
in making the evidence conform to 
Mendelian expectations. Bateson can 
only suggest that polydactylism “is 
perhaps due to a dominant factor which 
321 
