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-work 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 medusz is well exhibited in a tank 
lined entirely with black basaltic 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 power stations. Elsewhere the 
power is chiefly derived from gas engines. In the engine-rooms 
machinery is usually found in duplicate, one 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 white 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- 
