BAL'ANOGLOS'SUS (t k. po.x.pos, baanos, acorn, gland -yX(7icrcra, glossa, tongue). A re markable worm-like invertebrate animal. now generally regarded as in some way related to the probable ancestral form of the vertebrates. Two or three genera form the sole family of the ()vier Enteropneusta and the class Hemieho•da (or Adeloehorda). The body is long and slen der, and, some distance in front of the middle, is banded by an elevated ring, called the collar, from the front of which springs the somewhat tongue-shaped proboscis. (See illustration on plate of ASCIDIANS, etc.) Back of the collar, on each side of the body, are series of vertical slits opening through both the body wall and the wall of the alimentary canal. Water taken into the mouth passes out through these open ings and aerates the blood. The slits therefore function as gill-slits; and they are supported by 'chitinous' rods, like the gill-arches of Amphioxus. Projecting forward from the an terior upper side of the (esophagus is a short eartilaginous rod, which helps support the pro boseis. This apparently corresponds to the noto chord of the embryo of the higher vertebrates, and• because of its incomplete condition in Bal anoglossus, the name Hemichorda is given to the class The species of Balanoglossus (and allied genera) are found buried in the sand of the sea shore in shallow water in various parts of the world. They have been taken on both coasts of
America. on the Pacific north to Alaska. on the European side of the Alediterranean, in the East Indies. in the Bahamas. and on the south shore of Jamaiea. Most of the known species are small and dull-colored. but some of the West Indian species are over a foot in length and half an inch in diameter, and are brightly colored with red and yellow. There are generally little heaps of excrement about the entrance to the holes in which Balanoglossus lives. All the species have a musky odor, which is strong enough to indicate their presence to any one familiar with the smell. Sometimes it is so strong as to be highly disag.recatiie. Many of the species have a complicated metamorphosis in their development, the pelagic bell-shaped larva being known as a tornaria. It resembles superficially the larval form of some of the echinoderms, and for that reason some zoologists have sought for evidence of relationship between that group and the Ilemichorda. It is generally believed now, however, that the nearest living relatives of the Ilemichorda are to be looked for among the Ascidians. Compare AMPRIOXIJS; and CRORDATA. For illustrations see AsCIDIAXS.