Soma (Gr. soma, body), the body considered apart from the germ-cells.
Spermatid (Gr. sperma, seed), a cell resulting from the last division of the germ-cell in spermatogenesis. It transforms into the spermatozoon.
Spermatocytes (Gr. sperma, seed; kytos, cell), cells concerned in the maturation divisions of the male germ-cells.
Spermatogenesis (Gr. sperma, seed; genesis, origin), the development of spermatozoa from primitive sex-cells.
Spermatogonium (Gr. sperma, seed; gonos, generation), a primordial sperm-cell.
Spermatozoon (Gr. sperma, seed; zoon, animal), the functional male sex-cell.
Spindle, a fibrous organ formed in indirect cell-division.
Spireme (L. spira, coil), a characteristic stage preliminary to indirect cell-division in which the chromatin material of the nucleus appears in the form of a skein of filaments.
Stereotropism (Gr. stereos, solid; tropē, turning), defined, [p. 198].
Sterilization (L. sterilis, barren), deprivation of reproductive power. For methods, see [p. 322].