58 THE IMITATION, IN CLOSED CASES, OF 
vessel contained twenty gallons of water, and in it 
I placed ten or twelve gold and silver fish, in com- 
pany with several aquatic plants, viz. Valisneria 
spiralis, Pontederia crassipes, Papyrus elegans, 
and Pistia Stratiotes, which plants, by means of 
their vital actions, as had long been well known, 
maintained the purity of the water, and, as in the 
atmosphere, kept up the balance between the 
animal and vegetable respirations. Placed in the 
centre of my fern-house and nearly surrounded 
by rock work (rising five or six feet above the 
margin of the vessel, clothed with Adiantum and 
other lovely ferns, and partially overshadowed 
with the palmate leaves of Corypha australis, the 
plants and fish continued to flourish for years, 
prior to their removal to Clapham in 1848. The 
only enemy I had to contend with was a species 
of Vaucheria, which, from its rapid growth, re- 
quired to be kept constantly in check. My 
friend, Mr. Bowerbank, always alive to scientific 
inquiries, followed up these experiments with 
equal success, but substituted stickle-backs and 
minnows for the gold fish.* 
The plants were removed about three years and 
a half ago, from the case just described, to a house 
prepared for them at my new abode at Clapham. 
* Mr. Warington, who subsequently experimented upon the same 
subject, states that he found it necessary to introduce a few snails 
( Limeus stagnalis) to get rid of a slime produced by the decaying 
leaves of Valisneria spiralis. 
