THE AUSTRALIAN NATURALIST. 195 
ait THE AQUARIUM: ITS HISTORY AND 
“MANAGEMENT. 
By H. B. Frvcku. 
(Continued from p. 176.) 
And the conditions under which an Aquarium must be con- 
ducted are: 
The water used, whether salt or fresh, must not be changed, 
and it must not be added to, except to supply deficiency caused 
by evaporation or accidental loss. f 
The animals must be any or all which by means of gills or 
by having 4 respiratory function distributed over the surface of 
their body, possess the power of extracting oxygen dissoived in 
the water. : 
TJ might mention here that only the illuminating rays of the 
sun cause the plants to give off oxygen, not the heat or other 
rays. 
Dr. Priestly, another Hnglisiman, discovered oxygen, the in- 
visible gas which supports animal life and keeps everything in 
nature pure. , 
Priestly did more; he ascertained that it is the plant-life, both 
land and water, which, under the influence of light, emitted this 
gas, and he was the first to lay down the law upon which the 
existence of an Aquarium depends. Dr. Priestly was the one 
to lay down the law, but W. A. Lloyd was the first to main- 
tain an aquarium by combining plant and animal life; yet for 
some years before, a barber in London was unknowingly keeping 
an aquarium, in the most scientific manner imaginable, and. this 
led up to the discovery by Mr. W. A. Lloyd. 
One day W. A. Lloyd dropped into a barber’s shop, and 
noticing a fishbowl on the windowsill in which the water was 
perfectly clear, of course put the question, “How often do you 
clange the water?” The answer was, “Never now. I have had 
these two fish for about two years. I used to change the 
water whenever it became dull, and the fish came to the surface 
gulping for air, perhaps once or twice a week in summer, less 
frequently in winter. But since I have put this piece of coral, 
as a decoration, into the bowl (a piece of Brain coral the size 
of a fist) I have found the water to remain.clear for a longer 
period, and eventually it remained always clear, so that I have 
not changed the water for many months.” He added the only | 
