Arm-spines, of Ophiothrix fragilis, [479];
of Ophiuroidea, [491];
of Ophiothrix, [492];
of Ophiacantha, [492];
of Ophiopteron [492]
Aromatic compounds in relation to nutrition and antisepsis, [36]
Arthropods, hosts of Gregarines, [97] f.
Articulata, [595]
Ascitic dropsy, Leydenia associated with, [91]
Ascon, [185]