in Salinella, [96];

in Polychaeta, [278] f., [279], [280], [282], [340];

in Oligochaeta, [374], [375], [377];

in Phylactolaemata, [496];

in embryos, [365], [511]

Fissurella, as host, [298]

Flabelligera, [334]

Flame-cells, in Leptoplana, [13];

in Thysanozoon, [25];

in Triclads, [41];