Octobothrium, [56], [73]

Octochaetus, [358], [384]

Octocotylinae, [73]

Octotrocha, [221]

Odontosyllis, reproduction of, [278];

as host, [297].

Oecistes, [205], [206], [221]

Oenonites, [302]

Oesophageal glands, [271], [358]

Ogmogaster, [73]