(β) Gill-sacs opening by small pores. _Balanoglossus_, Delle Chiaje. (ii.) Genital wings hardly developed. _Glossobalanus_, Speng. (_b_) Liver-sacs, synapticula and nerve-roots absent. HARRIMANIIDAE (i.) Proboscis long; one proboscis-pore. _Dolichoglossus_, Speng. (ii.) Proboscis short; two proboscis-pores. (α) Two pairs of genital wings. _Stereobalanus canadensis_, Speng. (β) No genital wings. _Harrimania_, Ritter. The name _Balanoglossus_ was introduced by Delle Chiaje in 1829 for _B. clavigerus_ (Fig. 1, A), from the neighbourhood of Naples. As Spengel has shown, its etymology has been much misunderstood. The second half of the name refers to a fancied resemblance between the Balanoglossus, with its largely developed genital wings, and the tongue of an ox. Βάλανος means "acorn," and it has usually been supposed that this name was suggested by the resemblance of the proboscis, projecting from the collar, to an acorn in its cup, a view which finds its expression in the {18}name "Eichelwurm" used by German zoologists. But the idea expressed by Delle Chiaje was really a similarity between the collar of _Balanoglossus_ and the outer shell of _Balanus_, the barnacle or "acorn-shell" found everywhere on rocks between tide-marks. [Illustration: FIG. 8.—Metamorphosis of Balanoglossus, probably of _Balanoglossus biminiensis_ Willey, Bahama Islands. All the figures are magnified to the same scale (× 14). A, fully developed free-swimming larva, or _Tornaria_, side view; B, commencement of metamorphosis, side view; C, later stage, dorsal view. Increase in size takes place after this stage; _a_, anus; _b.c_^1, body-cavity of proboscis; _c_, collar; _c.r_, transverse ciliated ring; _d.p_ (in A), dorsal pore (= proboscis-pore), seen also in C on the left side, just behind the reference line _p.c_; _e_, eyes and sensory thickening of skin (in A); _g_, gill-pore; _g.s_, gill-sacs, developing as outgrowths of the alimentary canal; three are already present in B, but are better seen in C, in which they are still without openings to the exterior; _l_, postoral part of the longitudinal band of cilia; _l_′, its praeoral part; both _l_ and _l_′ are produced (in A) into tentacles, over which the band of cilia is looped; the groove in the middle of the figure, between _l_ and _l_′, conducts the food by the transverse groove to the mouth (_m_); _p.c_, blood-space of proboscis and pericardium ("heart" of larva); _s_, stomach. (After Morgan).] DEVELOPMENT.—The free-swimming, larval stage of Balanoglossus is known as _Tornaria_ (Fig. 8, A). Several distinct forms of the larva are known,[27] although it is not yet possible to refer them with certainty to their respective adults.