ae Cc. H. DANFORTH 
and owls. Mr. Fuertes was unable to find any indication 
whatever of brachydactyly in any of these birds. 
In the case of the domestic pigeons on the other hand, the 
writer has found somewhat the same condition that occurs in 
hens. ‘Swallow’ and ‘pouters’ both of which are booted, often 
show short lateral toes. Among ‘muffed tumblers’ also heavily 
booted, several specimens were found to have the third and 
fourth toes fully webbed, and I have been informed that the 
same condition sometimes obtains in ‘pouters.’ Davenport (’09, 
pp. 29 to 36) describes a similar condition in a strain of fowl. 
It is not clear whether all of his syndactylous specimens were 
also booted but the fact that the first cases arose in breeds that 
are normally booted, is probably significant. In another flock 
of fowl, related to those here described and having so far as 
known no syndactyly in the ancestry, a pair of brachydactyl 
birds produced two syndactylous chicks of the type described by 
Davenport. These cases suggest that syndactyly like brachy- 
dactyly may represent an arrest of development, occurring in 
the former case a little earlier than in the latter, and that the 
two conditions may be dependent upon a single factor. 
While the suggestion of linked determiners cannot be entirely 
ignored as a possible explanation of the results obtained, 
there is still further evidence against such an interpretation. 
This rests chiefly on the fact that there is a correlation between 
the degree of booting and the index of brachydactyly. Despite 
wide fluctuations, this fact is brought out by averaging the 
indices for the different grades. After excluding the two ex- 
treme cases with indices of 70 and 120 the average index for 
each group is as follows, grade 1, 93; grade 2, 91; grade 3, 89. 
If the two extremes are included, they tend to raise the value 
of grade 1 and lower the value of grade 3, thus accentuating 
the differences. Such a result is not easily explained on the 
assumption of two independent determiners but, on the con- 
trary, strongly suggest that the association is due to some- 
thing more than a chance proximity of the determiners in a 
chromosome. 
