n 
Warren Harmon Lewis 40% 
stained in haematoxylin and congo red. The sections were cut either 
five or seven and one-half microns in thickness. 
TSxtS 
ee Sess 
Zi = 
meee fe NS 
} aN Se wnad DP ara ry AA had SCN 
2. Oe a ee 25 
See eae Je oe 
=, 44 ‘ 
Sph. ~? UNE 
< 
4 ‘ 
EB: 
Fie. 2. Radial section through the optic cup of a chick 9 days, 19 hours old. 
Magnified 180 diam. (., cornea; £., ectoderm; Sph., sphincter bud. 
WANDERING PIGMENTED CELLS DERIVED FROM THE EPITHELIAL BUDS 
OF THE PIGMENT LAYER OF THE OPTIC CUP. 
The time at which the pigment and the wandering cells of the optic cup 
begin to appear varies considerably in different individuals, as does also 
the time of origin of the epithelial buds we are to especially consider. 
In a chick nine days and nineteen hours old (Fig. 2) the beginning of 
this budding process is clearly seen. Projecting from the outer surface 
of the pigment layer are numerous elevations, mostly in the region 
