90 NEW YORK ZOOLOGICAL SOCIETY. 



The Berlin aquarium, with 50 exhibition tanks of varying sizes, 

 is constructed in the grotto style. The tanks have a water 

 capacity of 100,000 litres. 



As a rule the exhibition tanks of these aquariums are lined 

 with rock-work on both sides and back, the rock-work frequently 

 commencing well forward and being piled to the surface in re- 

 ceding tiers, the different ledges of rock being especially effective 

 in the exhibition of anemones. In some cases pillars of rock are 

 constructed with good effect. Rock-w^ork being reflected from 

 the still surface often produces excellent grotto-like effects. 

 The bottoms of the tanks are of rock, gravel, or sand, according 

 to the species exhibited. 



At Berlin the collection of medusae is well exhibited in a tank 

 lined entirely with black l)asaltic columns. 



The introduction of rock-work permits of varying the appear- 

 ance of the different tanks perhaps more than could be secured 

 by the collections exhibited. Cobble-stones and volcanic rock are 

 often used. 



In most European aquariums the pumps are operated by small 

 electric or gas engines, the machinery being reduced to a min- 

 imum. At Naples no boilers are in use, the electric engines being 

 connected by wires with distant pow'er stations. Elsewhere the 

 power is chiefly derived from gas engines. In the engine-rooms 

 machinery is usually found in duplicate, Sne set being held in 

 reserve. 



Three kinds of tubing are in use : hard rubber, or vulcanite ; 

 iron pipes, porcelain-lined ; and soft lead pipes. The last is re- 

 ported as satisfactory for sea water, although from its soft nature 

 it is available only in the smaller sizes. 



The labeling of the collections in public aquariums is done in 

 various ways, the labels usually resting on the ledges in front 

 of and below the glass. They are often placed under glass frames, 

 and where several species are exhibited in one tank they are 

 identified by means of colored plates and paintings. In some cases 

 the labels are painted on w^hite tiles, the different species being 

 shown in colors on separate tiles. Where several species are 

 kept permanently in one tank their identity is sometimes shown 

 by paintings on ground glass hung near the top of the tank. 



At the Naples aquarium labels are not used, the tanks being 

 numbered to correspond with descriptions in the guide book. 



Owing to the fact that European aquariums are either ad- 

 juncts to biological stations, or have other attractions than their 

 purely aquarium collections, it was somewhat difficult to ascer- 



