LIMB REGENERATION IN SALAMANDERS CONT:tOLS 997 EXPERIMENTALS PARALLEL (a) wibe (b) Fig, 1—-Regeneration of control doubled stumps (neither limb irradiated) and experimental doubled stumps fright stump irradiated). [From J, C. Oberpriller, J. Exp. Zool., 168: 427 (1968).] the most lateral lines intersected, and no regenerate was produced, Part b shows that, when the experimental stumps werein a parallel position, a single hand was produced, apparently from the unirradiated limb, which was still exerting its longitudinal control, When the stumps were at an angle, the same phenomenon is seen. The regenerate that forms is produced by the unirradiated stump; the irradiated limb neither regenerates nor exerts any interference on the regenerating Mmb, Jean Oberpriller'! reasuned that, if X rays do obliterate lines of control, an X-rayed limb sewn to a normal limb at an angle would not interfere with the regeneration of the normal limb, This proved to be true (Fig. 2), This tells us that X rays destroy the operation of linear Oo st nel be ' i ee