Stereotaxy, [20]

Sterilisation of colonial cells in Volvox, [129]

Sternata, [554]

Sternum = Plastron, q.v.

Sterraster (an aster with very numerous actines soldered together by subsequently deposited silica, which extends almost to their extremities), [224]

Sterrula, [341]

Stewart's organs, of Cidaridae, [531];

of Echinothuriidae, [531];

of Arbaciidae, [531], [539];

of Diadematidae, [538]