26o 



NATURE 



\Atig. 6, 1874 



A MARINE AQUARIUM FOR INLAND 

 STUDENTS 



A COMMITTEE of the British Association was last 

 year appointed to make some inquiries into the 

 best mode of preserving delicate marine organisms 

 during life, the question being whether the injection 

 of a fine stream of air into the tank in which they are 

 living would be as efficient as, or better for this purpose 

 than, a jet of running water. Dr. Hubrecht, of the 

 Hague, has furnished Mr. Ray Lankester with the follow- 

 ing account of a contrivance worked with great success 

 by Prof. .Selenka, who has recently given up his chair at 

 Leyden, on account of malaria, and taken a similar post 

 at Erlangen. 



A point of the greatest importance for those who 

 study marine animals and who want to keep them alive 

 for a certain time, is the way to keep a limited supply 

 of sea-water fresh and in good condition so as to sus- 

 tain life in the objects of their researches. Plven in those 

 vast institutions on the coast at Brighton, Naples, &c. 

 where the inhabitants of the ocean exhibit their splendours 

 to the eyes of the public, and where there would seem to be 

 no difficulty at all in changing and refreshing the sea- water 

 at any given moment, this point requires more attention and 

 care than is ordinarily supposed, and the success of an 

 aquarium often depends upon the more or less ingenious 

 method by which the refreshing of the water is brought 

 about. Especially important is a free access of atmo- 

 spheric air, which must enter into solution and sustain the 

 respiration of the different inmates. 



To attain this end on a small scale in a laboratory 

 situated at a distance from the sea-coast, with glass vessels 

 of various sizes instead of tanks, and a small barrel of 

 sea-water, which must suffice for a considerable time, the 

 following system, adopted by Prof. Selenka, first in Leyden 

 and at present in Erlangen, gives the most satisfactory 

 results. 



A receptacle for fresh water of about 2 cubic ft. or larger 

 is placed in some spare corner, two stories higher than the 

 room in which the aquarium is situated. By means of 

 a siphon reaching to the bottom, the water can be put 

 into communication with a tube leading to the lower 

 floor. A tap enables one to regulate the quantity of water 

 flowing through the siphon. Immediately behind the 

 bend of this and fastened to the side of the receptacle, a 

 so-called Bunsen's aspirator eftects the distribution of air- 

 bubbles in the water streaming down. This instrument 

 simply consists of a tube in glass or gutta percha, with an 

 opening as large as a pin's head. The water now con- 

 tinues its way downward through a series of glass tubes 

 of no great width, fastened to nails in the walls by 

 strings. 



This system of tubes, to be had at a very small cost 

 and labour, leads the water into a second receptacle in the 

 same room with the improvised aquaria. It consists of 

 a cylinder in zinc of about three feet by one in diameter 

 placed upon a wooden stool ; a large tap at the bottom 

 permits its being emptied into a pail. In the lid three 

 small tubes form a communication with the exterior, each 

 of them, as well as the whole apparatus, being closed by 

 taps as hermetically as possible. One of these is put 

 into commimication with the above system of tubes which 



descend to the bottom of the receptacle. The second, 

 to which no interior tube is fastened, is in communication 

 with a pair of bellows which permit the creation of an 

 initial atmospheric pressure in the reservoir. Instead of 

 the bellows a simple tube, half india-rubber, half glass, 

 may do as well, the pressure then being obtained by 

 simple blowing with the mouth. The function of the 

 above apparatus is clearly that of compressing the atmo- 

 spheric air in the zinc receptacle by means of water de- 

 scending from a certain height. This compressed air is 

 now used for the refreshing and providing with oxygen 

 of the sea-water in the dilTerent smaller vessels. 



A third tap in the lid of the zinc reservoir per- 

 mits the air to escape into a glass bell, where a small 

 mercury manometer indicates the amount of pressure, a 

 detail which may, however, be omitted. In the perforated 

 stop of this bottle from six to twelve hermetically 

 sealed glass tubes— shellac is best for sealing them, 

 india-rubber for the stop itself- -are ready to provide the 

 difterent vessels with a supply of air. With this view india- 

 rubber tubes, which can be shut up by glass staves, form 

 the continuation of the glass ones. When made ready 

 for use, a spring screw applied to this india-rubber tube, 

 regulates the quantity of air flowing out, while a special 

 end-piece conducting the air-bubbles into the vessel with 

 sea-water is pushed into the open end of the tube. 



Those end pieces form an important part of the appa- 

 ratus and may give rise to a great economy of the force 

 required, when by some well-adapted combination their 

 effect is multiplied. 



In order to obtain the greatest advantage from the air- 

 bubble which, when the apparatus is put into working 

 order, rises through the sea-water in the vessel into which 

 one of the tubes is brought, it is desirable that it should 

 present as large a surface as possible to the water ; making 

 the contact more perfect and the dissolving process 

 easier. 



A so-called vulcanised rose, with numerous fine pores, 

 is for this purpose fixed to the extremity of the tube on 

 the bottom of the vessel. This may be replaced by a 

 simple india-rubber stop which has been applied to the ex- 

 tremity of the tube, and into which extremely fine glass 

 tubes — easily got by pulling out a thicker one before the 

 blowpipe and cutting it to the required lengths — have 

 been inserted. Or we may take two flat circular pieces 

 of vulcanised india-rubber connected together, and fix 

 into the border of the lower one a series of such fine 

 glass tubes disposed like the spikes of a wheel, care being 

 at the same time taken that the communication be rnain- 

 tained between the hollow part of this india-rubber disc 

 to which the hair tubes correspond and the glass tube 

 providing the air. 



To make the effect in the water still more complete, a 

 small water wheel (the paddles of which are made of thin 

 half- spheres of glass, the axis of a vulcanised tube re- 

 volving round a glass st.ave) may be placed above the 

 rising stream of air-bubbles, which put the wheel in a slow 

 rotation, and cause in this way a constant movement 

 of the particles in the sea- water, a circumstance which 

 cannot but be favourable. 



Nearly the whole of the apparatus described above 

 may be made at home, and can be had at very little 

 cost. It is of great efficiency and keeps the sea-water in the 



