The order of the Lophobranchii is in many respects too curious and interesting to be passed over in silence. Here the gills, instead of being as usual ranged like the teeth of a comb, are clustered into small filamentous tufts placed by pairs along the branchial arches; the face projects into a long tubular snout, having the mouth either at its extremity, as in the Hippocampus and in the Pipe-fishes, or at its base, as in the Pegasus of the Indian seas; and the body is covered with shields or small plates, which often give it an angular form, and encase it as it were in jointed armour. But the most interesting feature of their economy is the pouches in which the males of the most characteristic genera carry the eggs until they are hatched. In the hippocampi this provision for the safety of the future generation, which strongly reminds one of the kangaroo or the opossum, forms a perfect sack, opening at its commencement only; in the pipe-fishes it is closed along its whole length by two soft flaps folding over each other. Another peculiarity of these interesting little fishes is the independent motion of their eyes, the one glancing hither and thither while its fellow remains motionless, or looks in different directions. This phenomenon of _double_ vision, which was long supposed to be peculiar to the chameleon, is, however, not confined to this singular reptile or to the hippocampi and pipe-fishes, but has been found by Mr. Gosse to exist likewise in the Little Weever (_Trachinus vipera_), in the Suckers (_Lepidogastri_), a small family remarkable for the power they possess of attaching themselves to stones or rocks by means of an adhesive disk on the under surface of their bodies, and in several other fishes.
When imprisoned in an aquarium, few subjects of the deep display more intelligence or afford more entertainment than the little _Hippocampus brevirostris_, or Sea-Horse.
"While swimming about," says Mr. Lukis,[P] "it maintains a vertical position, but the tail, ready to grasp whatever meets it in the water, quickly entwines itself in any direction round the weeds, and, when fixed, the animal intently watches the surrounding objects, and darts at its prey with great dexterity. When two of them approach each other, they often twist their tails together, and struggle to separate or attach themselves to the weeds; this is done by the under part of their cheeks or chin, which is also used for raising the body when a new spot is wanted for the tail to fasten upon afresh."