Orthonectides, [120], [126];

figure of, [127];

degeneracy of, [130], [131], [141], [152].

Orthoptera, duration of life of, [39].

Ostracodes, parthenogenesis of, [294], [325];

polar bodies of, [350].

Otostoma Carteri, fission of, [148].

Palingenia, sub-imago stage of, [19], [40].

Paludinidae, length of life of, [56].

Pandorina, [202], [248];