Plessis, du, on Tetrastemma lacustre, [101] n., [118]

Pleurocotyle, [73]

Pleurotrocha, [224], [226]

Ploesoma, [212], [225]

Ploima, [202], [203], [212], [213], [216], [220], [223], [226], [227]

Plumatella, [493], [494], [499], [503]-505, [518], [519];

protrusion of polypides, [499];

statoblasts, [499], [502], [503];

larva, [512]

Podal membrane, of Spionidae, [322]