On the structure and behaviour ofFritillaria(Tunicata: Larvacea)

INTRODUCTION Rather little is known of the behaviour of larvaceans, although they are of great importance in the sea as one of the few groups able to exploit the nanoplankton. Of the two larvacean groups, oikopleurids have received most attention: the behaviour of Oikopleura dioica has been studied in detail by Gait (1972, Ph.D. Thesis, University of Washington, Seattle), and some notes on the electrical correlates of behaviour have been given by Gait & Mackie (1971) and by Bone & Mackie (1975) for O. dioica and O. labradoriensis . Much less is known of fritillariid larvaceans and, apart from the brief notes on behaviour by Fol (1872) and by Lohmann (1899) in the course of their classical histological investigations, which were extended by Salensky (1904) and Martini (1909), the only recent investigation of living fritillariids is that of Fenaux (1961) who described the remarkable mode of action of the pyloric cilia.