AQUARIUM, 3 



to proportion the one to the other, we succeed iti 

 maintaining, on a small scale, the balance of animal 

 and vegetable life. Other less important benefits 

 result from this arrangement; the creatures love 

 retirement and shelter, and this they find in the 

 umbrageous fronds; they delight to roam and to 

 play and to rest in the feathery tufts, and not a 

 few find their favourite food in the delicate leaves 

 of the submerged herbs. 



On the other hand, the plant is indebted to the 

 animal for some of its supplies. The carbon, with 

 which its solid parts are built up, is derived from 

 the carbonic acid which is thrown off by animals 

 in the process of breathing ; — a poisonous gas which 

 would soon vitiate the water were it not taken up 

 and appropriated by the plants. 



Such, then, is the principle on which the Aqua- 

 rium is founded ; and any conditions under which 

 it can be carried out will serve, provided of course 

 they be suitable in other respects to the liabits of 

 the animals and our purpose in keeping them. I 

 now proceed to other details on the practical 

 management, so far as I am able, from my own 

 experience, and that of not a few of my friends, 

 to give them; premising that I have at present 

 (April, 1856), at my residence at Islington, one 

 marine tank full of animals and plants in the 

 highest condition, the water in which, though as 

 clear as crystal and quite colourless, has never 

 been even removed from the vessel since it was 

 first put in, two years and two months ago. I 

 have, also, other tanks and vases, which are from 

 two years to one year old. The successful esta- 

 blishment of these has not been achieved without 

 some failures and losses, which yet must not be 

 b2 



