384 Mr. W. Thompson on Marine Vivaria. 



should be only about 6 inches water over the ledge ; the inclilied 

 plane I would have represent the zones of the sea^ the ledge 

 should represent high and low-water mark; I should fasten 

 battens across the incline, in order to attach stones and weeds at 

 different levels, and also sand ; as plants as well as animals, it is 

 well known, affect different levels. I may mention amongst 

 plants, Chylocladia articulata, which, is a beautiful species, but must 

 be left dry occasionally. I propose also that a tap be fixed at 

 one end of the tank, so as to draw off gradually as much water 

 as will leave uncovered the ledge at the top of the incline, the 

 ledge to remain uncovered a short time every day ; this I intend 

 to represent the tides, and the advantage I expect to derive from 

 this plan is : — First, we should give those species, such as 

 Chylocladia, Corallina, amongst plants, and Littoral Crustacea and 

 Testacea, as also the Nudibranchs, which are left dry by the tide 

 twice a day, a near approximation to their state of freedom ; and 

 secondly, the water when poured back, which I propose it should 

 be, would freshen up the water in the tank on the same principle 

 that at sea, they stir up the water casks to freshen the water. I 

 propose a Vivarium of this construction, only in the case of but 

 one being used. I am, however, convinced, the far better plan 

 would be to have separate tanks, but all fitted with taps. I 

 should suggest that for the strictly littoral species the tank 

 should be only a foot in depth, and the bottom on such an in- 

 cline that about 2 inches of water should lie left for about half 

 its length, and in this tank the chief plant should be Fucus 

 serratus. I think the larger and more voracious carnivorous 

 MoUusca, such as Buccinum undatum, should be kept in a tank 

 by themselves, as they can be easily fed on Mytilus edulis, Patella 

 virgata, or indeed on offal ; and with them you might place the 

 Starfish, Decapoda, that is the larger Macroura, the Anomoura 

 and Brachyura. These might easily be fed ; and with respect to 

 food generally, the carnivorous mollusca we see can be provided 

 for : the vegetable feeders will be amply supplied by the plants 

 and Confervse. But this is not the case with the Bivalves, some of 

 the Zoophytes and Nudibranchs, but more especially the bivalves ; 

 they will exist some time without food, but it would be more 

 satisfactory to know that this cruelty was not inflicted upon them ; 

 the greater number of the bivalves bury themselves, and most of 

 them swallow mud and sand and decayed vegetable matter, pro- 

 bably on account of the animalculse and other minute animals 

 they may obtain. What is then to be done in their case ? I admit 

 the difficulty and cannot solve it : you must either procure their 

 food, or exclude them from the vivarium ; and as they generally 

 burrow, I fancy they will be no great loss to the sight-seeing 

 public. As to the Starfish and Sca-Urchins they are essentially 



