Apsilus, [201], [212], [213], [214], [221]

Arabellites, [302]

Arachnidium, [532]

Archiannelida, [241];

anatomy, [243] f.;

nerve cords, [255];

development, [243], [245]

Archigetes, [5], [74], [76], [91];

significance of, [77]

Area, of zooecium, [523], [524]