{6}[Illustration: FIG. 1.—Forms of Balanoglossus. A, _Balanoglossus clavigerus_, Eschsch., Naples, × ½; B, _Glandiceps hacksi_, Mar. (incomplete), Japan, × 1; C, _Schizocardium brasiliense_, Speng., Rio de Janeiro, × 1; D, _Dolichoglossus kowalevskii_, A.Ag., Chesapeake Bay, × 1. _a_, Anus; _ab_, abdominal and caudal regions; _b_, branchial region; _c_, collar; _g_, genital region; _g.p_, gill-pore; _g.w_, genital wing; _h_, hepatic region; _m_, position of mouth; _p_, proboscis; _t_, trunk. (A, B, and C from Spengel; D from Bateson.)] _Balanoglossus_, the largest genus now recognised by Spengel, appears to be practically world-wide in its distribution; _Schizocardium_ is recorded from both sides of S. America; _Glandiceps_ from the Atlantic, the Mediterranean, Japan, and the Indian Ocean; _Spengelia_ from the South Pacific; and other species from the White Sea to New Zealand. The habitat is usually sand or gravelly sand, in which the animal forms a kind of tube by means of the abundant mucus secreted by its skin. _Dolichoglossus kowalevskii_ (Fig. 1, D), according to Bateson,[9] lives between tide-marks at a {7}depth of about eight inches. The greater part of the body is coiled in an even, cork-screw-like spiral, while the anterior end, including the front part of the branchial region, is maintained in a vertical position. The posterior end is also kept upright, and can be moved up and down in a vertical shaft opening on the surface, thus enabling the animal to eject the undigested sand from its anus. The coloration of Balanoglossus is often brilliant. That of _D. kowalevskii_[10] is as follows:—The "proboscis" (cf. Fig. 1, B, _p_) is yellowish white; the "collar" (_c_) is brilliant red-orange (especially in males), with a white ring posteriorly; the "trunk" (_t_), the subdivision of which into "branchial," "genital," "hepatic," "abdominal," and "caudal" regions is better indicated in other species (Fig. 1, A, _b_, _g_, _h_, _ab_), is orange-yellow, shading to green-yellow in the semi-transparent caudal region. The genital region is grey in females and yellow in males, a sexual difference in colour being common in Enteropneusta. The hepatic papillae of other species may be bright green. The odour of _D. kowalevskii_ resembles that of "chloride of lime with a faecal admixture," while that of _Balanoglossus aurantiacus_ suggests iodoform. All Enteropneusta are said to have a more or less offensive smell. A species of Balanoglossus is known to be intensely phosphorescent.[11]