Figure 4.

These graphs show how the fraction of BrdU+ cells in the brain (i.e. tectum, telencephalon) VZ increases with survival time after BrdU application in chickens and quail at (a) 11% of incubation (i.e. ED2–3) and (b) 22% of incubation (i.e. ED5). The slopes of these lines are inversely proportional to cell cycle duration. Furthermore, the LIs saturate at similar levels in the two species. These data indicate that (a) brain precursor cells cycle faster in chickens than in quail at 11% of incubation. (b) However, brain precursor cells cycle at a similar rate in chickens and quail at 22% of incubation. Diamonds, chicken brain; filled circles, quail brain.