THE MARINE AQUARIUM. 93 
cells of tube worms, and of the openings of the shells of 
mollusks, and thus suffocate the inmates, and insure their 
own death by the putrescence that ensues upon the demise 
of their victims. 
Sulphuretted hydrogen.—When the death of an animal 
occurs, the water soon gets putrid; the stones assume a 
rich brown tint, the sides of the vessel lose their bright- 
ness, and an effete odour indicates the cause of the dis- 
turbance. 
Preservation of the Water.—To those who live near 
the sea it is an easy matter to change the water, as soon 
as it shows signs of disorganization, but since the 
majority of those who will consult this work will have to 
depend on Mr. Belton’s marine salts, it is necessary that 
T should suggest in what way, and in the best manner, 
the water may be preserved, not only to avoid the expense, 
but the trouble attending a new supply. Charcoal is the 
grand restorative, purifier, and preserver; and for this 
department of aquarium management may be regarded as 
the ne plus ultra. 
In the second Chapter of this part of the work I have 
described the process necessary in preparing artificial 
water by means of the filter. Now, whatever happens, 
set the filter to work, it will revive exhausted stock by 
aeration, destroy sulphuretted hydrogen by the contact of 
the water with the charcoal, and remove all fragments of 
decayed weed, flocculent threads given off by anemones, 
and restore the whole to strength and purity. I repeat 
what I have already said more than once, that the neces- 
sity for changing the water is a proof of injudicious 
