Pre-Cambrian Echinodermata, [623]

Precious Corals, [326], [352]

Pre-oral, cilia, [139];

ridge, [139];

undulating membrane, [139]

—see also Prae-oral

Preyer, on the response of Asteroidea to stimuli, [446] f.;

on the intelligence of Ophiuroidea, [488] f.

Primary spine, of Echinus esculentus, [506];

of Cidaridae, [532];