The attractions of invertebrate nervous systems have long been appreciated by neurophysiologists. Indeed some of the milestones in our understanding of nervous systems have their foundations in experiments done on invertebrate preparations, typified by the role of the squid axon in dissect- ing the events that constitute the action potential. More recently we have seen how the relatively simple nervous system of Aplysia has permitted new insights into the molecular mechanisms of memory and learning. Neurochemists, however, have not been enthusiastic about invertebrate tissues as their...