Call it sleep -- what animals without backbones can tell us about the phylogeny of intrinsically generated neuromotor rhythms during early development.

A comprehensive overview is presented of the literature dealing with the development of sleep-like motility and neuronal activity patterns in non-vertebrate animals. it has been established that spontaneous, periodically modulated, neurogenic bursts of movement appear to be a universal feature of prenatal behavior. New empirical data are presented showing that such' seismic sleep' or 'rapid-body-movement' bursts in cuttlefish persist for some time after birth. Extensive ontogenetic research in both vertebrates and non-vertebrates is thus essential before current hypotheses about the phylogeny of motorically active sleep-like states can be taken seriously.