Studies on the cephalochordates of madras coast.

The U-shaped endostyle of Amphioxus is known to secrete mucus. When the endostyle is separated from the two sides of the pharyngeal wall, the secreted mucus travels backwards along the groove without being lifted up. However, in an intact specimen the mucus is lifted up along the sides of the gill bar and spreads over the pharyngeal epithelium. As the mucus travels vertically upwards it acts as a moving 'fly paper' to gather particles brought in by the water current. A feature of interest is the observation that the secretion of mucus is enhanced when the concentration of suspended particulate matter is increased. Such copious mucus production helps the formation of mucous sheets between the gill bars causing a reduction of gill slit area available for the outflow of water. In such cases the beating of cilia is masked and the ciliary beat could clearly be seen when the mucous sheets are being torn. It has been suggested that the mucus plays an important role in regulating the volume of water filtered besides the ciliary activity which is said to be under nervous control. [ABSTRACT FROM AUTHOR]