Colon. Proximal most part of large intestine of vertebrates, excluding the narrower, terminal rectum. In amniotes and some Aphibia, but not in fish, clearly marked off from small intestine by valve, and probably largely concerned with absorption of water from faeces.

Colostrum. A liquid with a high content of nitrogen, antibodies, and vitamins that is secreted from the mammary glands before and just after giving birth. The change of secretion from colostrums to proper milk takes place gradually during the days after birth.

Colour blindness. Any disorder of vision in which colours are confused. The most common types is red-green colour blindness. This is due to a recessive gene carried on the X chromosome (see sex linkage), and therefore men are more likely to show the defect although women may be carriers. It results in absence or malfunctioning of nerve cells sensitive to coloured light (cones) in the retina of the eyes.

(3) Bundle of nerve fibres connecting right and left sides of brain or spinal cord in vertebrates. (4) Nervous cords uniting ganglia of Mollusces.

Coma. A tuft of hairs attached to the taesta of a seed and used in wind dispersal.

Commensalism. It refers to an association between two species in which one gets the benefit and the other is unharmed or unaffected.