OF SEA- ANEMONES. 71 



or river, and not sea-water, must be added to the 

 residue, or the animals will die, being unable to con- 

 tinue their existence in the state of inclde to which 

 they have been subjected. 



With regard to the aerating — i. e. the partial puri- 

 fying of the "water — we may adopt one or more of 

 four methods. First, we may employ sea-weed for 

 the purpose. Mr. Gosse recommends this pro- 

 ceeding in his ' Devonshire Coast;' he says- that, as 

 plants in a healthy state give out oxygen (under the 

 influence of light) and take m carbon, and as ani- 

 mals reverse the process, a balance may be kept up 

 between a due proportion of anemones and sea- 

 weeds in any receptacle. Certain it is that sea- 

 weeds give out oxygen under light, — the bubbles on 

 the fronds of the Ulva are very striking, — and 

 therefore they must aid in purifying the water ; but, 

 on the whole, I am inclined to think that when sea- 

 anemones are kept for purposes of observation the 

 sea-weeds are better omitted, for the decaying matter 

 which they originate, and the film of green which 

 they produce, is hardly compensated by the aerating 

 power which they possess. For purposes of orna- 

 ment, or as an interesting experiment in this curious 

 balance of power, a few plants of green Ulva {latissima 

 or lactuca) and of red Delesseria (sangubica) or 

 Iridcea (edulis), or of the curled and tinted Carrageen 

 moss, may be advantageously placed among the 

 stones of our tanks. 



