Modified from: 
Kimmel et al., 1955. 
Developmental Dynamics 203:253-310. Copyright © 1995 Wiley-Liss, Inc.
Reprinted only by permission of Wiley-Liss, a subsidiary of John Wiley &
Sons, Inc.
Fig. 24.   The optic primordium is well formed at the 9-somite stage (13.5 h).   Left side Nomarski view, dorsal to the top, anterior to the left.  In the fashion of the neural rod itself, the optic primordium is a solid tissue at this time, not a hollow vesicle.  A hint of a seam run across it that precedes development into the optic cup.  Scale bar: 50 µm.

Figure 24