The rules governing the establishment of specific neural connections during embryogenesis are being investigated in chick embryos by anatomical and electrophysiological techniques. The preparations studied are the ciliary ganglion and the lumbosacral spinal cord. In the latter, the development of peripheral projection patterns by both senory and motor neurons is being investigated under normal conditions and following a variety of embryonic manipulations (cord reversals, limb bud reversals etc.). Central connections are being assessed onto motoneurons following such experimental manipulations as well.