Boyle in many experiments. Roses are bleached by sulphur, and may be restored to their first state by other acids; roses are turned green by the smoke of tobacco.
LII.
WORMS, INSECTS, FISHES.
636.
With regard to creatures belonging to the lower degrees of organisation, we may first observe that worms, which live in the earth and remain in darkness and cold moisture, are imperfectly negatively coloured; worms bred in warm moisture and darkness are colourless; light seems expressly necessary to the definite exhibition of colour.
637.
Creatures which live in water, which, although a very dense medium, suffers sufficient light to pass through it, appear more or less coloured. Zoophytes, which appear to animate the purest calcareous earth, are mostly white; yet we find corals deepened into the most