Respiration, in Nereis, [252];

in Chaetopoda, [272];

in Gephyrea, [416]

Retepora, [479], [515], [518], [527]

Rhabdites (rods), of Leptoplana, [11], [12];

in Polyclads, [29];

in Triclads, [37];

absent in parasitic Rhabdocoela, [45];

in Temnocephala, [53], [54]

Rhabditiformae, [137]