success of the institution. Subdivision of the work makes possible a routine of duties that proceeds as regularly and orderly as on board a man-of-war, and this is necessary, for now and then the sinuous eel plays his pranks and stops some outlet, threatening the institution with flooding.
No less important is an intimate knowledge of the fishes themselves. When fishes of different kinds are put together in a tank, they often war with each other until one kind is exterminated, and sometimes fishes of the same kind will not tolerate certain individuals. In one of the gallery tanks may be seen a single angel-fish brought from Bermuda four years ago. It is of surpassing beauty, but it kills every other angel that is put in the tank with it. No matter how
many of the curious, triangular, hard-bodied trunk-fishes are put together, one is always made the butt of the rest, and worried by them until it dies, and then another is pestered, until but one is left. In many of the tanks where the fishes dwell in harmony together, there will be one that dominates all the others. It seems to demand a certain deportment and procedure from the others, and is always on the alert to exact compliance. The familiar story of the Mexican shepherds who know each individual in their vast flocks finds its parallel in the intimate knowledge of their charges possessed by the men who care for the tanks at the Aquarium, and this enables them to keep a delicate touch on the daily life in the tanks that contributes largely to the success recognized by the public. For instance, a slight uneasiness in one of the fishes in a certain
