76 



SCIENCE-GOSSIP. 



[Apeil 1, 18GG. 



of Corallina, (Ilea, waft. Conferva, together with some 

 small animals, such as Mollusks, Annelides, and a 

 Starfish. The whole continued to thrive during the 

 eight weeks through which the experiment was 

 made (and how much longer we are not told) with 

 the sea-water unchanged, and Dr. Johnston points 

 out these facts clearly. But the proportionate 

 measurements of the vessel are not given, nor the 

 amount of light permitted to fall on it, nor the 

 temperature of the water ; and it may safely be 

 assumed that if the glass was not deep in propor- 

 tion to its width, the large surface exposure to the 

 atmosphere thereby obtained would have enabled 

 the animals to live for a time without any vegeta- 

 tion visibly introduced in a grown state, as the 

 Doctor describes ; so that such plants were not 

 necessary, and in a short period — a few days or a 

 week or so — other plants would have made their 

 appearance, under the influence of light, from spores 

 invisibly contained in the water. Yet these con- 

 siderations must not be allowed to interfere with 

 the merit of Dr. Johnston ; but still, for all that, 

 the object he had in view was to prove the vege- 

 tability of Corallina officinalis, and the animals 

 associated with that plant were only incidental. 



The next step onwards— that of introducing 

 plants for the avowed purpose, stated beforehand, of 

 preserving the purity of the sea-water and of sus- 

 taining the animals in health— is due to Mrs.Thynne, 

 who experimented in London in the autumn of 

 1846, on living madrepores. This lady caused her 

 animals to be the principal things considered, the 

 plants being secondary or incidental ; whereas with 

 Dr. Johnston the contrary was the case, and I think 

 that much importance should be attached to this 

 fact, and to a specific intention, previously laid down, 

 and designedly carried out, for the first time, by 

 Mrs. Thynne. 



Mr. Ward, in 1S41, made an aquarium of fresh 

 water in a twenty-gallon earthenware vessel con- 

 taining plants and gold and silver fish, but whether 

 he did this with the intention of carrying out the 

 compensating principle, or whether he introduced 

 it only as a green-house ornament, I cannot say; 

 but Mr. Robert Warington's first fresh-water aqua- 

 rium, set up in the summer of 1849, and his earliest 

 marine aquarinm, made in the beginning of 1852, and 

 Mr. P. H. Gosse's first sea-water arrangements, also 

 begun in January, 1852, were all set going with the 

 balancing principle distinctly in view, as was also 

 a small fresh-water aquarium of Dr. Bowerbank's at 

 about the same period. But the greatest first 

 effort at aquarium-keeping was the public one in the 

 Zoological Gardens, Regent's Park, London, com- 

 menced in May, 1853 (the introductory experiments 

 aud trials in connection with it having been carried 

 on since the previous autumn), and to that is 

 certainly due nearly all the popular interest in 

 the subject which has since been manifested. 



It was in the commencement of 1851 that the 

 Society's then Secretary, the late Mr. D. W. 

 Mitchell, first pointed out to me a tank which 

 he said disproved the necessity of vegetation in 

 aquaria, as the vessel in question had been standing 

 for a long time with healthy animals in unchanged 

 sea-water, and, by accident, no plants had ever been 

 put in. In this, Mr. Mitchell was both right and 

 wrong, for there had been no occasion to introduce 

 plants, and a great quantity of microscopic vegetation 

 had everywhere made its appearance in the tank ; 

 but because it was microscopic, it was by him 

 erroneously not regarded as the useful form of 

 plant-life it proved itself to be ; and this observation 

 of Mitchell's led me gradually to avoid the intro- 

 duction of ready-grown vegetation (save in a few 

 instances), but to depend on the action of light to 

 develop plants on the rock-work of aquaria in course 

 of time. This also led to many changes of form and 

 proportions of tanks, and to the dependence for 

 picturesque effect on the form of the rock-work 

 itself (thus covered with vegetation in situ) rather 

 than on the groupings of introduced plants according 

 to the rule which obtained when aquaria first 

 became general. I believe that such introduced 

 plants do harm rather than good in nine cases out 

 of ten, because at present we do not know how to 

 keep them alive, and their decaying remains do 

 mischief. It is far better to employ self-grown 

 plants which may be exactly regulated by admitting 

 or excluding light, instead of endeavouring to 

 control their too luxuriant growth by the use of 

 scavengering snails which do their office very in- 

 completely. I am much amused when I remember 

 that just before this period of reform, 1S57, when 

 customers of mine purchased some additional animals 

 for aquaria, a lot of plants were also bought at the 

 same time to balance the newly-introduced creatures ! 

 It is singular to reflect that the early observers — 

 Trembley, Baker, Ledermuller, Ellis, Dalyell, 

 Power, and all others who kept aquatic animals 

 for considerable periods in glass vessels, must at 

 some time or other have exposed such vessels to 

 light for periods sufficiently long to cause plants to 

 appear in the water and keep it pure ; yet it never 

 came across their minds to turn such accidents to 

 good account, but they went on, as before, changing 

 the water and cleaning out the vessels. To do 

 otherwise never occurred to Mons. Lucaze-Duthiers, 

 even, when he kept Corals {Cora/Hum rubrum) in 

 confinement on the coast of the Mediterranean 

 during the last four or five years. Connected with 

 this is a curious statement made by M. Lucaze- 

 Duthiers, to the effect that he had a branch of coral 

 which fiourished in captivity very well, till, being 

 removed to Algiers, it remained contracted, because, 

 as the experimenter thought, the water supplied to 

 it was taken from the outside of the harbour, but 

 when dipped from ihe inside, where it Mas less 



