Nat. Neurosci. 2, 254– 259 (1999)

On page 257, Fig. 4d was printed without its red or green components because of a printer's error. The correct version is below.

(c) At the position of the lateral extension, two axons are seen continuing beyond the expanded region of the recently spread growth cone. (d) Serial sections containing axons were collected for electron microscopy, allowing tracing of individual axons. Fiduciary marks, predominantly organelles and large vesicles, aided in the determination of individual axons in multiple sections. The three axons are color coded, and tracings from each section are shown. The green and black axons were in the lead and were both induced to collapse. The red axon trailed, with its growth cone spread on the culture substratum after the lead growth cones collapsed. (e) Maximum number of axons that can be identified in a single section at any given position along the retinal ganglion cell fiber. Three individual axons are observed proximal to the lateral extension, and no more than two axons are observed distal to this point.