Marine creatures are more delicately constituted than fresh-water ones; and they demand more care, patience, and oversight to render the marine aquarium successful.

Our unbalanced aquariums.

A curious case has been given by Professor Möbius, of a pike, separated by a plate of glass from an adjoining aquarium stocked with fish, and who often dashed himself with such violence against the glass in trying to catch the other fishes, that he was sometimes completely stunned.