414 Wandering Cells and Muscles from the Optic Cup Epithelium 
similar to the sphincter pupillary buds. The peripheral portion of the 
muscle would thus seem to be formed by these iris buds and the inner 
portion near the pupillary margin by the large Sp A coh 
buds arising from the pupillary margin. see 
Fie. 11. Fie. 13. 
Fie. 11. From achick 13 days old. Mag. 260 dia. C. P., ciliary process. 
Fic. 12. From achick 13 days old. Mag. 130 dia. 
Fic, 18. From a chick 13 days old. Mag. 150 dia. 
THE FORMATION AT THE PUPILLARY MARGIN OF BUDS FOR THE M. 
SPHINCTER PUPILLAE. 
The first indication of the formation of the sphincter buds at the 
pupillary margin occurs during the seventh day by a gradual disappear- 
ance of the pigment of the outer layer for a short distance from the 
pupillary margin. Soon a distinct line separates this area from the rest 
of the pigment layer, and by this time all the pigment is lost and the bud 
is easily recognized. It becomes thicker than the neighboring portion 
of the pigment layer and stains exactly as the inner layer with haema- 
toxylin and congo red. The line of demarcation between the bud and 
the pigment layer becomes sharp and oblique and in places the two appear 
to separate (see Fig. 15). This process proceeds faster on one side of 
the eye than the other. At first the processes do not form a continuous 
bud around the pupil, but a series of them separated at fairly regular 
intervals by areas where the formation of the buds is going on at a 
slower rate. By the tenth day, however, these intervals have developed 
so far as to form a continuous bud band about the pupil. As the bud 
band continues to enlarge and thicken it overlaps more and more the 
