On The Origin of Species by Charles Darwin Chapter 16 Page 42

They are usually green, but sometimes brightly coloured.

SERRATURES. — Teeth like those of a saw.

SESSILE. — Not supported on a stem or footstalk.

SILURIAN SYSTEM. — A very ancient system of fossiliferous rocks belonging to the earlier part of the Palaeozoic series.

SPECIALISATION. — The setting apart of a particular organ for the performance of a particular function.

SPINAL CORD. — The central portion of the nervous system in the Vertebrata, which descends from the brain through the arches of the vertebrae, and gives off nearly all the nerves to the various organs of the body.

STAMENS. — The male organs of