408 Wandering Cells and Muscles from the Optic Cup Epithelium 
between the iris and the ora serata. These elevations consist of epithe- 
lial cells containing nuclei and pigment granules. ‘The pigment is simi- 
lar in color, nearly black, to that in the pigment layer, but the granules 
are very close together and give the buds a darker appearance than the 
adjoining pigment layer. In this eye there were no buds much farther 
advanced than those seen in Fig. 2. There were but very few wan- 
dering pigment cells, occasionally one here and there, and their pigment 
was of the same color and character as that in the epithelial cells of the 
optic cup. Fig. 3, from the tan- 
gential section of the pars ciliaris 
retinae of a chick ten days old, 
shows epithelial buds projecting far- 
ther from the pigment layer but still 
connected to it by a thick pedicle. 
The pigment in the buds is of the 
same character as in the pigmert 
layer, the staining of the protoplasm 
Fig. 3. Tangential sect'on through the : 
optic cup of ¢ chick 10 daysold. Mag.190 and the character of the nuclemas 
a i ee of ciliary muscle anlage; well as the continuity of aeuumae 
with the pigment layer indicate 
quite clearly their epithelial origin. There are many other buds in this 
eye in various stages, some more advanced with small pigmented 
branches and narrow attaching pedicles, buds which are about ready to 
separate from the pigment layer and wander farther into the connective 
tissue stroma where there are numerous wandering pigmented cells. 
Many and perhaps all of these I believe have come from similar bud- 
dings of the pigment layer. The pigment of these wandering cells 
seems to be identical so far as optical appearances are concerned with 
that in the pigment layer. The nuclei, the staining and the general ap- 
pearance of these cells, aside from the pigment, indicate that they are 
other than the ordinary branched mesenchyme cells. As the buds con- 
tinue to grow the knob-like ends may send out branches and elongate or 
may remain spherical for a while, at least after the disappearance of 
the connecting pedicle between it and the pigment layer. 
In Fig. 1, from a chick 6 days and 13 hours old, is a bud with a nar- 
row pedicle and enlarged distal end. The bud is clearly a prolongation 
of the outer or pigment layer of the optic cup from near the choroid 
fissure and projects into the cleft heap of condensed mesenchyme. The 
enlarged distal end is to be found in the neighboring sections and consists 
of several cells with nuclei. The yellow brown pigment granules of 
similar character are present in the bud and in the pigment layer. This 
