342 H.:M. VernoD 



Iiitrodiiction. 



Some tbree years ago, it was suggested to me by Prof. Ray 

 Lankester, that an investigation into tbe conditions of life in marine 

 Aquaria, especially witb reference to tbe cycle of cbanges undergone 

 by tbe nitrogenous matter excreted into tbe water, and also as to 

 the effects of aeration, migbt afford results of botb tbeoretical and 

 practical importance. Tbe work I tben bappeued to be engaged 

 upon, concerning tbe »Effects of Environment on tbe Development 

 of Ecbinoderm Larvse«', bore very closely on tbese questions, but I 

 bave not bad an opportunity to continue tbese experiments, and 

 extend tbem in tbe particular direction suggested by Prof. Lankester, 

 until tbe present time. 



Tbe problem of tbe maintenance of marine aquaria in a state 

 of equilibrium by tbe iutroduction of various forms of plant life, to 

 remove tbe carbonio acid and nitrogenous matter excreted by tbe 

 animals, is no uevv one. Sucb au aquarium on a very small scale 

 appears to bave been first successfully maintained by Dr. Johnston 2, 

 as early as tbe year JS42. Subsequently Warington^, by tbe iutro- 

 duction of bealtby pieces of various algse, as tbe Ulvse, Enteromorpba) 

 and Cladopborse, whicb bad carefully been left in contact witb tbe 

 nodules of flint or cbalk from wbicb they were growing, found it 

 possible to maintain a state of equilibrium between the animai and 

 vegetable life in a small tauk for montbs, or even years. It was 

 of course necessary to add a little distilled water from time to time, 

 to counteract tbe effects of evaporation, but otberwise no renewal of 

 tbe sea-water was required. Almost simultaneously witb Warington's 

 experiments, similar attempts at maiutainiug marine aquaria were 

 made by P. H. Gosse ■•. Red weeds, especially Chondrus crispus, 

 Iridea eduKs and tbe Delesserise, were found by bim to be more 

 favourable tban tbe green weeds, but be did not at first find it 

 possible to maintain bis aquarium for more tban a montb or two at 

 a time witbout tbe iutroduction of fresb supplies of sea-water. Sub- 

 sequently however, by tbe Substitution of green weeds for red, he 



1 Phil. Trans. 1895. B. pag. 577. 



~ History of British Sponges and Lithophyte.s. 1842. 



3 Gardeners Botanica! Matjazine and Garden Companion. Jan. 1852. also, 

 Ann. Mag. N. H. (2) Vol. 12 185;^ pag. 319 and Vol. 14 1854 pag. 366. 



4 Ann. Mag. N. H. (2) Vol. lü 1852 pag. 263. 



