Electrophysiological techniques and labeling with HRP are being used to determine how embryonic chick lumbosacral motoneurons repond to manipulations altering their original spatial relationship with their peripheral target. These include rotations of the limb, partial rotations or deletions of the spinal cord, and the addition of supernumerary limbs. These will allow us to determine which mechanisms are responsible for generating neuromuscular specificity during development. The effect of the peripheral target and motoneuron cord position on central connectivity will also be assessed by recording EMG's for muscles following similar manipulations.