The Zoologist — September, 1873. 3667 



and a few water-snails, Limnea peregra, and the smaller species of 

 Planorbis, in the water, and floating a little duck-weed on the 

 surface : then the glass was placed in the sun, so as to assimilate 

 the condition of the little captives as nearly as possible to what it 

 had been when in the ponds on Hampstead Heath in which they 

 had been hatched, and in which they were found. Treated thus 

 they continued alive and well, without change of water, and thus 

 J was enabled to continue the observations /or nearly two years.'''' 



Although in this passage the words " aquarium," " balance of 

 life," and " compensating principle" do not occur, it is very evident 

 that Mr. Bowerbank was aware of the use of vegetation in main- 

 taining life-supporting properties in stagnant water, and the neces- 

 sity also of imitating the natural conditions of the animals he 

 desired to keep therein. To this hour none of us have advanced 

 further with fresh water, and success only results from keeping these 

 objects steadily in view. Mr. Bowerbank's paper was finished on 

 the 1st of October, 1832, and was published at p. 239 of the 

 'Entomological Magazine' for April, 1833. I need scarcely say 

 that it placed the author at once at the head of all observers in this 

 branch of Entomological Science. I regard it as the best, if not 

 the first instance of thoroughly utilizing the compensation principle 

 of the fresh-water aquarium : plants to evolve oxygen, animals to 

 consume it. 



In the same year Professor Daubeny read, at the Cambridge 

 meeting of the British Association for the Advancement of Science, 

 a paper communicating the result of researches he was then 

 making on the subject of confining animals and plants together in 

 water, in the course of w^hich he established beyond dispute that it 

 was the illuminating and not the heating powers of the sun's ravs 

 which caused the evolution of oxygen from plants. He then went 

 on to say that the plants not only evolved oxygen but assimilated 

 carbon from the poisonous carbonic-acid gas which results from the 

 respiration of animals, decomposing it and rendering it harmless. 

 Finally, he asserted boldly " that the influence of the vegetable 

 might serve as a complete compensation for that of the animal 

 kingdom.^'' Thus he seems by inductive reasoning and possibly 

 by seeing the successful results in many parlours in London, 

 to have perceived as clearly, as he expressed happily, the theory 

 and practice of the aquarium ; but it must be recorded that 

 while everyone else was succeeding to admiration, Dr. Daubeny 



