on the dorsal surface of the ganglion immediately below the ectoderm, or of one larger median and several smaller lateral ocelli are found in the various species of _Salpa_. These eyes have in {105}most cases a retina formed of elongated cells, and a pigment-layer placed upon the ganglion. The so-called otocysts of _Salpa_ have been shown by Metcalf to be really glandular organs. They have been called lateral neural glands; they do not open at the dorsal tubercle, but separately into the pharynx. These lateral neural tubular glands have also been regarded as nephridia. The large spaces at the sides of the dorsal lamina (often called the gill or branchia of _Salpa_), by means of which the cavity of the branchial sac is placed in free communication with the peribranchial cavity, are to be regarded as gigantic gill-slits formed by the suppression of the lateral walls and small stigmata of the branchial sac. The alimentary canal at the posterior end of the "gill" consists of oesophagus, stomach, and intestine, with a pair of lateral gastric glands or caeca. These viscera along with the reproductive organs, when present, make up the "nucleus" (Fig. 66, _v_). [Illustration: FIG. 65.—Diagrammatic sagittal section of a "chain" _Salpa_. _an_, Anus; _at_, atrial aperture; _at.m_, muscles of atrial aperture; _atr.cav_, atrial cavity; _br_, branchial aperture; _br.m_, muscles of branchial aperture; _br.s_, branchial sac; _d.l_, dorsal lamina or "gill"; _d.t_, dorsal tubercle; _end_, endostyle; _ht_, heart; _int_, intestine; _l_, sensory languet; _mus.bds_, muscle-bands; _n.g_, nerve-ganglion; _oc_, eye-spot; _oe_, oesophagus; _ov_, ovary; _p.p.b_, peripharyngeal band; _s.gl_, neural gland; _stom_, stomach; _t, t′_, test; _tes_, testis; _z_, prebranchial zone. (After Herdman.)]