1. The peripheral nerve is probably essential for all stages of regeneration of thoracic limbs in the crustacean Asellus aquaticus. The inhibitory effect of denervation decreases, however, with the rate of regeneration itself.
2. When a limb reaches the functional stage denervation leads to some degree of disuse-atrophy, which masks the possible neurotropic effect on late stages of regeneration and on normal growth.
3. A limb denervated previously to amputation is capable of forming a regeneration blastema at the surface of amputation, and normal regeneration probably begins as soon as the regenerating nerve reaches that surface.
4. There is probably no general degeneration following denervation at any stage of regeneration or of normal growth, and growth is probably always resumed with reinnervation.