Figure 2. Treatment of cultured skin explants with cyclopamine inhibits feather bud elongation. Skin explants from stage 31 embryos were cultured for 3 days in the presence of HPCD (top) orHPCD containing 5µg of cyclopamine (bottom). In the control, the feather buds have elongated. In contrast, no feather bud elongation is apparent in the cyclopamine-treated explants, although the thickened placodes can still be visualized using dark field photography.