ABSTRACT
This chapter discusses the nervous system and sensory structures and outline aspects of molluscan behaviour and learning. The variety of configurations of the nervous system is paralleled by a diverse range of sense organs, many of which have independently evolved in each taxonomic group. The brachiozoan nervous system differs substantially from the molluscan nervous system. Todt et al. and Sigwart and Sumner-Rooney gave detailed accounts of the nervous systems of solenogasters. Monoplacophoran statocysts open to the anterior mantle groove by way of a narrow duct. Statocysts function as organs of balance and orientation and are found in all conchiferans. The euthyneuran heterobranchs possess several sensory organs in the cephalic region that have mixed functions, being in part olfactory and mechanosensory. A pair of cephalic tentacles is present in gastropods and perhaps monoplacophorans. Cephalic tentacles are found in most gastropods, although they are secondarily lost in some heterobranchs.
