112 Wandering Cells and Muscles from the Optic Cup Epithelium 
appear to extend over a period of several days from the eighth to the 
fifteenth day at least and probably for some time after this, but I have 
not as yet examined specimens older than the fifteenth day. The inten- 
sity of the process varies in different individuals, as will be seen from the 
table. The two specimens where buds occur without wandering cells 
would seem to indicate that the buds precede the occurrence of wander- 
ing pigmented cells. In the remaining specimens we see that where 
hut few buds are present but few wandering cells occur, or where no 
buds are present no wandering cells occur, and where there are numer- 
ous buds there are as a rule numerous wandering cells. 
M. SPHINCTER PUPILLAE BUDS FROM THE EPITHELIUM OF THE OPTIC CUP. 
Arising from the iris portion of the pigment layer are Jarge epithelial 
buds which appear to take part in the formation of the M. sphincter 
pupillae anlage. As will be seen from the table they appear later than 
those sphincter buds arising from the pupillary margin of the optic cup. 
Fig. 7 shows an iris bud which might perhaps break up into wandering 
cells or lose its pigment and take part in 
the formation of the sphincter muscle. 
There were a number of such buds in this 
Sph, 
22 ‘ EB. Sph' Sph. 
{ 
| | 1 ( 
Fie. 7. : Fie. 8. 
Fie. 7. From a chick 8 days, 12 hours old. Mag. 130 dia. 
Fig. 8. From a chick 7 days, 23 hours old. Mag. 130 dia. Sph’., sphincter mass 
from pigment layer. 
eye arising from just about the same position on the pigment layer, 
namely about half way between the pupillary end of the pigment layer 
and the ciliary process, and most of these seem to arise opposite the cil- 
lary processes and are thus arranged in a circle about the pupil at equal 
distances from its margin and aft fairly equal distances apart. Fig. 8 
shows another such bud attached by a slender pedicle and containing 
pigment. It does not seem possible to decide whether such a bud would 
develop into. wandering pigment cells or lose its pigment and form 
