April 1, 1S66.] 



SCIENCE-GOSSIP. 



Vo 



such a fact would most certainly have beeu told as 

 ouc of great interest. Neither is any mention 

 made of the reciprocating influence of plants and 

 animals upon each other (much less of the prin- 

 ciple being turned to practical account in vessels 

 containing creatures anil plants) in Trembley's 

 elaborate work in Erench on the Hydra, published 

 at the Hague in quarto, in 1741-, and which book 

 Ledermuller quotes. 



I may be excused for remarking, incidentally, 

 that to me, here, in Hamburg, surrounded with 

 every known aquarium improvement and luxury, 

 there is produced by contrast a very curious feeling 

 on looking at some of Trembley's beautifully exe- 

 cuted copper-plates, representing the collecting of 

 Hydras in the straight-lined canals, bordered by 

 prim avenues of trees, in trim ancient Dutch 

 gardens, and the conservation of the living animals 

 in cylindrical glass jars in the simple fashion of those 

 days. All is quaint, old-world-looking, and geo- 

 metrical, even to the square cut of the coat-tails 

 of the imperturbable collectors themselves. 



Neither was Baker (who wrote an English book 

 on the Hydra at about the same time), aware of the 

 compensating principle referred to, for he, as well 

 as his contemporaries, in giving directions for 

 keeping the Hydra in confinement, instruct that 

 the water shall be changed, either by emptying 

 what is in the vessels, or else by pouring in fresh 

 quantities and displacing the old water. Clearly, 

 therefore, these early manipulators knew nothing of 

 aquaria as we now understand them. And yet one 

 finds occasionally, in the course of one's reading, 

 statements to the effect that such-and-such a person 

 kept aquatic animals in confinement at a named date, 

 and that, therefore, the invention of aquaria should 

 date from that time. The first thing to be done in 

 such cases is to correctly define what an aquarium 

 is ; and according to my judgment it is any arrange- 

 ment by means of which certain animals are main- 

 tained in health in water which is never changed, 

 but which is permanently kept in a pure and 

 respirable condition for the animals by vegetation 

 growing in it and decomposing the carbonic acid 

 gas given out by the breathing of the animals, the 

 result of such decomposition being the production 

 of the oxygen gas which the animals require, and 

 the carbon which the plants need. Thus a balance 

 is kept up, and this may or may not be made more 

 certain and easy by giving the water a large surface 

 so as to enable it, in addition, to absorb still more 

 oxygen from the atmosphere; or it may or may not 

 be made still more safe by circulating the same 

 water from one vessel to another. The essential 

 points are, the same animals kept a reasonably long 

 time in the same water preserved pure for an inde- 

 finitely long time by the action of growing plants. 

 The animals must not be lung-breathers, that is to 

 say, they must not take in air direct from the 



atmosphere, but indirectly from it, through the 

 medium of the water in w 7 hich they live ; and the 

 animals which do this are aquatic creatures, both 

 fresh-water and marine, from sponges to fishes, 

 both inclusive, and including also a few reptiles, 

 of which an example may be found in the Proteus 

 (Proteus anguinus), which can breathe by both 

 lungs and otherwise, i.e., by gills, and which 

 is occasionally kept in aquaria. If this rigid 

 definition be applied, it will prevent the creeping in 

 of many errors. Eor example, according to the rule 

 laid down, a globe of gold fishes with the water 

 changed at intervals cannot be termed an aquarium ; 

 neither can any vessel in which any animals are 

 temporarily kept ; nor can a duck or seal pond be 

 called an aquarium, even if the water were to be 

 preserved unchanged, because the animals are lung- 

 breathers, and do not breathe through the water. 

 Nor can a fish-pond, whether it be out or in-doors, 

 be termed an aquarium if any but the same water 

 is allowed to flow in and out of it, even though the 

 fish are not lung-breathers. 



Madame Jeannette Power has deservedly obtained 

 much celebrity by her persevering and ingeniously 

 made studies of living marine Mollusks — chiefly the 

 Paper Nautilus (Argonauto argd) on the coast of 

 Sicily about 35 years ago, and these researches are 

 given to the world in a pamphlet (p. 76), published in 

 Paris, in 1860, and at page 2 and elsewhere Madame 

 Power says that in the year 1832 she invented 

 aquaria, wherein she studied the animals referred to. 

 But these aquaria, so called, were large cages 

 or open-work boxes, made so as to contain the 

 animals in the sea, and to prevent their escaping. 

 I have seen the drawings of these cages in Paris, 

 with their chains and anchors affixed to prevent 

 them from being washed aw-ay. Clearly, therefore, 

 these cages thus anchored off the shore at Messina 

 were not aquaria. But Madame Power had at that 

 period other vessels with animals, not in the sea, 

 but indoors; yet, as the water was changed 

 periodically, and plant life was not avowedly and 

 of aforethought depended upon to keep it pure, 

 these vessels could not be called aquaria. 



Then, as to Sir J. G. Dalyell. He kept living 

 aquatic animals in vessels in his house at Edinburgh 

 from before the close of the last century till nearly 

 the middle of the present one, but he continually 

 changed the water and cleaned out his receptacles ; 

 and yet, though he in this way amassed much 

 valuable knowledge, his not using the same 

 water and his knowing nothing of the influence of 

 plants to keep it pure, destroyed all claim to his 

 having kept aquaria in the strict sense of the word. 



In the year 1842, the late Dr. George Johnston, 

 in his "History of British Sponges and Lithophytes," 

 p. 215, tells how he at some period previous to this 

 date (1842), constructed a small marine aquarium in a 

 six-ounce glass jar, in which was placed some plants 



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