one neuron will only make synaptic contact with a unique target neuron? If less precise, within what range? Are the rules for specification that are operative in the embryo still operative at the same level of precision when connections regenerate in the mature organism? Are they still operative in dissociated tissue grown in culture? The second section of this volume contains reviews of morphologi­ cal studies of synaptogenesis and biochemical studies of synaptic com­ ponents. Can the morphology of developing cellular contacts provide clues about selectivity? Can the chemical components of synaptic junc­ tions be isolated and characterized? Do they include resolvable compo­ nents that mediate neuronal recognition? The third section contains studies seeking to identify the existence of specific molecules that might mediate cellular recognition. A major question here is whether molecules of this type even exist.