624 JOVRNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXVIII. 
and for this reason pendants were substituted as the wiring of these is far less 
liable to damage. 
The aeration of these tanks is dual, partly by the inflow of filtered sea-water 
from a high level reservoir, partly by means of an air compressor delivering air 
in a mist of tiny bubbles at the bottom of each tank. To obtain sufficiently 
minute division of the air stream, it is delivered under pressure through filter 
candles hung in the tanks. By this means, the water is kept so fully aerated 
that it is possible to maintain a permanent state of overcrowding seldom if ever 
found, even temporarily, in the open sea. Unfortunately it is not possible to 
regulate this super-aeration to suit the varjfing constitutiona' idiosyncrasies of 
every kind of fish. Some, in consequence, suffer from a disease that has 
been appropriately called ‘ gas-eye.’ It arises from an excess of air finding its 
way into the blood stream, by absorption through the gill-membranes ; the 
outward sign of the disease is the partial protrusion of the eye-balls. Many of 
the fish aff jjted ev^entually recover, and all do so quickly if transferred to ordinary 
sea- water. A proportion die either directly from what appears to be a form of 
asphj’xiation, or indirectly from the onslaught of the other fish in the tank, to 
whom the sight of a protruding eye-ball is the signal for attack ; the eye-ball in 
these cases is often plucked out and if the fish be small, it is often killed outright. 
The larger ones after losing an eye not infrequently recover and this accounts 
for the presence of quite a considerable number of the larger fishes in the tanks 
being short of one eye. The air circulation is effected by means of a manual 
air compressor which stores up compressed air in two cast iron cylinders, 
whence an outflow is led through tubing to the various tanks. The table 
aquaria successfully depend wholly on compressed air aeration, even in the 
hottest weather. 
The water circulation ai-rangements comprise three underground reservoirs 
which may be named A, B and C at the rear of the aquarium, a gravel filter bed, 
and a high level suppl}^ tank. A pipe from the sea margin conveys new sup- 
plies of sea water when required to the median reservoir A, whence it is pumped 
by hand into the filter ; from there it passes into the underground storage reser- 
voir B used normally for filtered water only. From this supplies are again 
pumped by a cooly into a high level iron tank, whence the water flows b}’ gravi- 
tation, controlled by stop cocks, to the several aquarium tanks. The overflow 
from these is at the surface, and flows back to storage reservoir C, to be pumped 
by hand into the filter bed, in order to be freed from impurities before entering 
again into circulation. Each tank is also provided with a clean-out pipe-exit 
at the bottom, for use when the tank has to be emptied for an}' purpose. The 
piping used is of galvanized iron, the stop cocks being of brass or gun metal. 
In spite of considerable corrosion, the original piping is still serviceable. 
The table tanks are of various types as the first patterns have been greatly 
improved upon of recent years. The most useful form is one where the base is 
composed of a single plank of teak (21 inches thick), carrying four stout up- 
right grooved pillars at the corners, into which the four glass plates forming the 
sides and ends are let. The grooving is puttied with the same material as 
in the larger tanks, and as an additional waterproofing precaution, a thick 
layer of asphaltum is poured hot over the wooden bottom on the inside. An 
ornamental wooden beading finishes off the upper edge of the tank and supports 
a protective cover-frame. 
The floor tank has not been a success as it has been found impossible to light 
it satisfactorily. Murrel and Gourami live well in it and the former have bred 
there several times, the parents watchfully guarding the nest ; they resent actively 
any prying into their domestic affairs on the part of visitors. The four rooms 
at the front of the building comprise two store rooms, a pump room, where the 
air compressor is located, and a curator’s room. At the rear of the building, an 
additional laborato has recently been built, as the need for such a convenience 
