Individuals of seven species of coleoid cephalopods (three species of octopus, three of squid, and one of cuttlefish), that were cultured and reared in laboratory aquarium systems, had a behavioral defect at hatching which was characterized by an inability to control orientation while swimming. These defective animals were designated as "spinners." An examination of statocysts from individuals of five of the affected species revealed abnormalities of the neuro-epithelial suprastructures: absence or malformation of the statolith of the gravity receptor system and absence of the cupulae of the angular acceleration receptor systems. The sensory epithelia did not differ from those of normal animals, nor did the synaptic structures and relationships, when examined both with scanning and transmission electron microscopy. The abnormalities were compared with congenital defects of the neuropeithelial suprastructures of the vestibular apparatus (especially in mammals). The defects observed in statocysts of spinner animals are thought to be the result of environmental causes, such as the temperature or chemistry of the seawater in the transportation vessels or rearing systems, rather than genetic causes.