620 Aquaria: Their Past, Present, and Future. [ October, 
tank by Leete Edwards and Norman’s machinery, the speed of 
which is accelerated (Çi. e., the oxygenation is quickened) when 
the water is slightly turbid from an excess of organic matter. 
All this I have explained more at length in the Official Hand- 
book to the Crystal Palace Aquarium, and in Observations on 
Public Aquaria, both published at the Crystal Palace. It is this 
power of oxygenating, or consuming, or burning, at a low tem- 
perature, termed by Baron Liebig “ eremacausis,” + which ex- 
presses the real work done in an aquarium, and the force neces- 
sary to do that work. Even our thick beds of sand and shingle 
at the bottom of each tank are so fully charged with air that 
one thrust of a stick will release a pint of it in bubbles. This is 
a source of purification and health quite unknown till recently. 
Consequently the floors of our tanks (excepting the sea anemone 
tanks) are as speckless and as free from the blackness caused by 
sulphureted and carbureted hydrogen gas, as on the day they 
were laid down in 1870. . If we have an excessive growth of 
sea-weeds anywhere, we turn in a shoal of gray mullet (Mugil 
capito), which nibble it down close, like sheep in a field of grass. 
This leads me to say that at present we do not know how to 
grow the higher marine algee, the red, the brown, or even the 
green kinds, at will. Sometimes I succeed, but always by chance, 
not knowing why. : 
Of the general influence of aquaria on zodlogy we have oe 
ous evidence in Mr. Gosse’s most excellent Manual of Marie 
Zoölogy for the British Isles,” published in two volumes, m 
1855-56, in which the author enumerates 1785 species, from 
sponges to fishes, and of which he figures 779 genera, always 
preferring to draw from living animals whenever possible, Now, 
as at that period a larger number of aquarium animals had 
passed through his hands than through those of any other person, 
he may be presumed to have, up to then, seen more of them 
alive than any one else. Yet he enumerates only 201 as having 
been drawn from life, as he avowedly preferred doing, and of 
these but a dozen were fishes, others being, for the most part, 
small creatures, or those which are easily maintained and do not 
need large tanks and elaborate machinery. But during the 
twenty years which have elapsed since 1856 I have seen 
handled and had under my care, in England, France, and we 
many, about 433 species of British marine animals, of which 1 
were fishes. 
1 From the Greek “ to remove by burning, or by fire.” The words « caustic” and 
“ cautery ” have the same derivation. ; 
pie S a a a 
