R8 was unique in that Dl function is absolutely required, unlike the R2/3/4/5 cells that are nearby during R8 selection. Frequency of Dl^- R8 cells (0/88) was significantly lower than 3/88 seen for R2 or R5 cells (95% confidence limit; binomial distribution).

Based on the higher recovery of Dl^- R4 cells and R7 cells, it is possible that that Dl expressed in each of the other photoreceptor cells may play some role in normal photoreceptor recruitment(see text). It is unlikely that possible sibling relationships of other R cells to R8 is sufficient to explain their reduced frequency in normal ommatidia, because in this experiment many Dl^- clones include only one cell.

Dl is required in R3 cells only if the neighboring R4 cell is Dl⁺. Two Dl^- R3 cells were observed in ommatidia where R4 was also Dl^-

The total includes R4 cells in chirally reversed ommatidia that were otherwise constructed normally

The total includes R7 cells that adopted R1/6 morphology in ommatidia that were otherwise constructed normally