3. Limb Disc surrounded by Limb field What happens when limb disc is removed? Is all ectoderm competent? Old vs. Young AER Which tissue determines type of limb?

4. What is Mesoderm producing? Wingless mutant Polydactyl mutant Which tissue controls Programmed Cell Death? Meso Ecto Duck leg + Chicken leg  ? Chick leg + Duck leg  ? What triggers Programmed Cell Death? Tadpole metamorphosis

5. Regeneration Epimorphosis vs. Morphallaxis Limb regeneration - Blastema What is necessary for limb regeneration? Denerve then amputated  ? Amputation  Blastema formation then denerve  ? Nerve transplants in animals which normally lack regeneration: Newborn Opposum 1. Hindlimb Amputation  ? 2.Supplemental nerve tissue  ? Electrical fields

6. Hydra – regeneration gradients Head Activator vs. Head Inhibitor Role of nerves Budding - level of HA at gastric bud