Schneiderman 9422143 During the development of the neuromuscular system, a series of complex interactions are involved in the specification of the pattern of innervation of any specific muscle. This research is designed to elucidate the sequence of events that result in the development of the appropriate connections between neurons and muscles. To address this problem a novel invertebrate system will be employed. The innervation of muscles will be studied during the process of metamorphosis, when degenerating muscles are being replaced with newly formed muscles. In particular, the role of hypothesized "muscle pioneer cells" in neural specification will be examined. The results of this research will provide basic information about the major steps involved in the development of connections between neurons and muscles, as well as insight into the plasticity inherent in the developing and regenerating neuromuscular system.