Pergens, on Polyzoa, [500]
Perichaeta, [351], [357], [358], [372], [381], [381] f., [388], [394], [403]
Perichaetidae, [357], [362], [380]
Perienteric, blood-sinus, [252]
Perionyx, [381]
Perissogaster, [383]
Peristome, [481], [482], [522], [524]
Peristomial (tentacular) cirri, of Nereis, [248];
of Polychaeta, [263];
nerves to, [254]