The _Doris pilosa_ is a pretty white species of the same order; and the little black shining Nudibranch, _Runcina Hancoci_, is a pretty and interesting creature. But the handsomest of the Nudibranch or naked-gilled tribe, as the term might be Englished, is the _Eolis corronata_, which forms certainly a splendid ornament to the Aquarium. Its general colour is a pellucid indistinct tone, of pinkish hue, the papillæ or branchiæ are in clusters, and the central canal is of a rich crimson. Different parts of the surface reflect the brightest metallic colours, and the whole creature has a very gem-like appearance. In captivity it is very active. Another species of _Eolis_ has the power of making a singular clicking noise, like the _Tritonia_. The _Aplysiæ_, or Sea-Hares, have been unenviably celebrated among their congeners as containing a virulent poison. The species common in the Mediterranean, _A. Leporinæ_, furnished the venom with which the infamous Locasta destroyed the enemies of Nero; and with which she eventually prepared, at the tyrant’s request, a draught for himself, but which he had not the courage to swallow. The British species, _A. hybrida_, might probably be kept in confinement. Many of the Sea-Worms are very beautiful. The _Nereis bilineata_ is very brilliant, with its crimson body brightly marked by two white longitudinal stripes. The _Phyllodoce_ are a class of Sea-Worms, somewhat resembling the land Centipede, which form curious objects of observation when they are in search of food. Instead of spreading a set of tentacles, like some of the Zoöphytes and Molluscs previously described, they have the faculty of turning the cavity which forms the stomach inside out, like a stocking, the inverted organ protruding from its mouth to a considerable distance, which, when it becomes sufficiently covered with the minute Infusoriæ which form its food, is drawn in, assuming gradually its natural position, where it remains till the nutriment so introduced has been absorbed, when the operation is repeated.