In _Conchoderma aurita_ the ophthalmic ganglia are much smaller, and nearer to the supra-oesophageal ganglion, than in _L. fascicularis_. In _Alepas cornuta_ the ophthalmic chords run towards each other from the two distant and separate supra-oesophageal ganglia; and the ophthalmic ganglia, (instead of being quite separate, as in _L. fascicularis_,) are united by their front ends, and the two eyes instead of standing some way in front, with nerves running to them, are embedded on the double ophthalmic ganglion; the pigment-capsules here, also, have the shape of mere saucers, and are joined back to back, with the two lenses projecting far out of them. In neither sex of Ibla could I perceive that the eye was double. In _Pollicipes spinosus_ the ophthalmic ganglion stands in front of the single supra-oesophageal ganglion, and shows no signs of being formed of a lateral pair; the eyes themselves, however, differently from, in all the foregoing cases, are, though approximate, quite distinct. In _Pollicipes mitella_ I did not see the eyes; but the ophthalmic ganglion consists, as I believe, of a single globular one, placed exactly between the two globular, supra-oesophageal ganglia, all three being of nearly equal size. Professor Leidy does not mention the ophthalmic ganglia; hence I infer that in Balanus, which is a more highly organised Cirripede, they are fused into the supra-oesophageal ganglion. In all the genera, the double eye is seated deep within the body; it is attached by fibrous tissue to the radiating muscles of the lowest part of the oesophagus, and lies actually on the upper part of the stomach; consequently, a ray of light, to reach the eye, has to pass through the exterior membrane and underlying corium connecting the two scuta, and to penetrate deeply into the body. In living sessile Cirripedes, vision seems confined to the perception of the shadow of an object passing between them and the light; they instantly perceived a hand passed quickly at the distance of several feet between a candle and the basin in which they were placed.