Ratarula larva, [302]

Rathkea, [265], [270]

Ratio (Spencer's) between bulk and surface of organism, [14], [23] f., [31] f.

Reactions, chemical, of protoplasm and of vacuoles, [13];

motile, of Protozoa, [19] f.

Receptaculites, [207]

Receptaculitidae, [207]

Rectal caeca, of Asterias rubens, [439];

of Asteroidea, [459];

of Astropecten, [459];