PHALACROCLEPTES VERRUCIFORMIS GEN. NOV., SP. NOV., AN UNCILIATED CILIATE FROM THE SABELLID POLYCHAETE SCHIZOBRANCHIA INSIGNIS BUSH

Phalacrocleptes verruciformis lives on the frontal surfaces of the prostomial pinnules of Schizobranchia insignis (Sabellidae). Delicate projections extended from its changeable inferior surface contact the epithelial cells of the host and probably serve as feeding organelles. Although it has no cilia at any stage in its life history, and probably no kinetosomes, P. verruciformis has both a macronucleus and micronucleus, and reproduces by binary fission in much the same way as most other ciliates; moreover, the sequence of nuclear changes involved in its conjugation fits the pattern for ciliates in general. The systematic position of this organism within the group of ciliates is uncertain. It is perhaps a suctorian which does not produce ciliated larvae. There is also a possibility, however, that it is related to the ancistrocomid thigmotrichs which parasitize the prostomial pinnules of sabellids.