[Illustration: FIG. 6.—_Schizocardium brasiliense_; transverse section through the branchial region, showing the great extent of the branchial part (_b_) of the pharynx; the oesophageal part (_o_) is reduced to a mere groove; _g_, gill-pore; _g.s_, gill-sac; _r_, reproductive organ; _s_, synapticula (cf. Fig. 5); _t_, tongue-bar. The muscles of the body-wall are not indicated: in other respects the figure corresponds with Fig. 4, except for the absence of genital wings in this region of the body. (After Spengel.)] At a certain distance behind the branchial region, the alimentary canal in _Balanoglossus_ and _Schizocardium_ is produced into a series of outgrowths, into which food does not pass. These "liver-sacs" give rise to corresponding folds (Fig. 1, A, _h_) {14}of the dorsal body-wall, a conspicuous external feature of the species in which they are present. The most interesting peculiarity of the digestive tract in this region is the existence, in certain species, of pores, possibly vestigial gill-slits, leading from it to the exterior. NOTOCHORD AND SKELETON.—The structure compared by Bateson with the Vertebrate notochord is a hollow dorsal outgrowth of the alimentary canal of the collar-region (Fig. 7, _n_). Near its origin it is slender, but in the proboscis it dilates into a comparatively large organ, which in most cases retains its cavity. Its cells have a vacuolated appearance, which recalls the fine structure of the Vertebrate notochord. In _Schizocardium_ and _Glandiceps_, the organ is produced into a slender "vermiform process" (_v_), which extends nearly to the tip of the proboscis. [Illustration: FIG. 7.—_Schizocardium brasiliense_; longitudinal, median section through the proboscis, the collar, and the first part of the trunk; _b_, main blood-space of the proboscis; _b.c_^1, _b.c_^2, _b.c_^3, first, second and third body-cavities; _c.m_, circular muscles of proboscis; _e_, epidermis; _l.m_, longitudinal muscles of proboscis; _m_, mouth; _n_, notochord; _n.s_, central nervous system, continuous with the subepidermic nerve-plexus (black) of the proboscis, and with the dorsal nerve (_d_); _p.c_, pericardium; _p.s_, proboscis-stalk; _s_, proboscis-skeleton; _v_, vermiform process of notochord. (After Spengel.)] The main support of the proboscis-stalk is the "proboscis-skeleton" (_s_), a Y-shaped organ whose median part lies beneath the base of the notochord, its diverging legs extending backwards along the outer side of the alimentary canal of the collar. The proboscis-skeleton, like the branchial skeleton, is a special development of the structureless membrane which is found at the base of the layers of cells {15}of Balanoglossus, and in most species it grows merely by the deposition of laminae of chitin from the notochord, and from the ventral epidermis of the proboscis-stalk.