Cell contact does not regulate putative RP2 fate in culture. (A, B) Low-power photomicrographs show contact-free putative RP2s after 48 h in culture, in the absence (A) or presence (B) of 20E. The putative RP2 in (A) is alive and that in (B) is dead. Note absence of neuritic contact with other neurons. (C) Histogram shows percentage of putative RP2s alive at 48 or 72 h (data pooled from Figures 7 and 8); n given above each bar. Among these contact-free putative RP2s, significantly fewer survived in cultures containing 20E (*P = 0.028; Fisher's exact test). Scale bar: 10 μm.