104 Cc. H. DANFORTH 
of brachydactyl specimens, having a relatively high index, may 
be overlooked even among late embryos. Among 90 embryos 
of ten days and over, 57 had long fourth toes; 33, short. Of 86 
young chicks, 55 had an index of more than 100 while 31 showed 
an index of 100 or less (brachydactyl). The totals for embryos 
and chicks are: out of 186 individuals, 112 normal, 64 brachy- 
dactyl. This is 36.4 per cent, which is intermediate between 
the percentages for booting and polydactyly. These character- 
istics behave in heredity quite differently from color and comb 
form which give results corresponding closely to the Mendelian 
expectation. 
EMBRYOLOGY OF BRACHYDACTYLY 
Since brachydactyly in poultry has not seemed to attract 
much attention (Anthony, ’99, states that he has seen specimens 
which showed four and six phalanges in their fourth toes), a 
fuller account of the condition may be entered upon at this 
point. Inasmuch as the shortening of the other toes is relatively 
slight and difficult to measure the fourth only will be considered. 
The skeleton of a normal foot is shown in figure 1, B. Digit IV 
has five phalanges, the terminal one bearing a nail. Among 
brachydactyl specimens, the fourth toe varies from a condition 
in which nail and all five phalanges are present with a total 
length equalling that of the second toe (but not exceeding it as 
in normal feet) to a condition showing complete absence of the 
nail bearing phalanx and only two remaining phalanges. Inter- 
mediate conditions are represented by toes with three or four 
well formed phalanges and by toes with the full number of 
joints but of considerably reduced length. The brachydactyl 
toes also varied from the normal in other characteristics such 
for example as the number of rows of scales. The two sides of 
the same individual were found to be very closely correlated. 
Among the 31 brachydactyl chicks that hatched, the index varies 
from 70 to 100, with an average of 89, which is identical with the 
index of the father. All of the specimens had the nail reduced 
and seven of them had only four bones in the toe as shown 
either by dissection or surface configuration (fig. 3). 
