BRACHYDACTYLY IN. THE FOWL 103 
to several feathers on the shank. Grade 3 stands for speci- 
mens with about twelve feathers on the shank, three or four 
on the lateral toe, and occasionally one or two on the middle 
toe. Grade 2 includes specimens intermediate between 1 and 
3. The distribution among the three grades was as follows: 
grade 1, 14; grade 2, 10; grade 3, 12. The father was grade 2. 
Out of a total of 129 chicks and embryos of thirteen days and 
over, 80 were normal and 49 booted,—38 per cent. Booting, 
EXIT. 
FLEX. 
Fig. 2 Sketches of cross-sections of comparable regions of the right shank 
from (A) nine-day and (B) eleven-day embryos, both of which were strongly. 
brachydactyl. Dr., down rudiment; Fzt., extensor group of tendons; Flez., 
flexor group of tendons; Mz., metatarsal cartilages. 
like polydactyly, does not give strictly Mendelian proportions 
(Hurst, 705, Davenport, ’09). 
E. Brachydactyly. In chicks with normal feet the lateral toe 
is about 10 per cent longer than the medial; in brachydactyly 
chicks it is of equal length or shorter. While the differences are 
only slight and in embryos difficult to measure a certain number 
of obvious cases can be recognized in nine-day specimens. From 
the tenth day on they are clearly distinguishable, probably in 
nearly all cases. It is possible, however, that a small number 
