694 ^-^^ POPULAR SCIEXCE MONTHLY, 



surface of the water, as these animals require a resting-place above 

 water. Small floats may be prepared for them by smearing a cork 

 with marine glue and sprinkling it with sand. When the glue has 

 dried, place the float in water and allow it to remain there for some 

 time before putting it into the aquarium. These animals have also a 

 disposition to rove, which must be checked by covering the aquarium. 

 The cover should be of glass and flat, with a large opening in the 

 centre. The cover is also advantageous to keep out dust. Mollus- 

 cous animals, as the horny coil-shell {Planorhis corneiis) and the pond 

 mud-shell {Limnea stagnalis)^ may be added. They are both to be 

 found among the grasses that grow in ponds and on the margin of 

 brooks. Such insects as the common water-spider {Argyroneta aqua- 

 tica), the large harmless beetle {Hydrous piceus)^ and the little whirli- 

 gig ( Gyrinus natator), can be introduced to advantage. Pugnacious 

 individuals, as the perch and the stickleback, though interesting, are 

 not desirable objects for a general aquarium. The best food for the 

 animals described is a little biscuit-powder kneaded into pills about 

 the size of a pin-head and fine shreds of raw beef cut with scissors. 

 The first should be fed once a day, the biscuit and meat being thrown 

 in bit by bit alternately. 



Fig. 5. 



Marine Aquarium (Side View). 



The marine aquarium must be supplied with sea-water taken not 

 less than a mile from shore, or from the middle of a large river. When 

 any is lost from the tank by evajyoration^ add fresh rain-water to sup- 

 ply the deficiency ; losses otherwise occasioned must be made good 

 by the addition of sea-water. Among the most curious and interest- 

 ing animals are the shrimp or prawn ; the smooth anemone (Actinia me- 

 semhryanthemum)^ one of the hardiest and most curious animals that 

 can be found ; the limpet {Patella vulgaris), with its shelly parasite the 

 barnacle (Balanus)\ the hermit-crab {Pagurus Bernhardus)\ the stone- 

 crab ( Cancer pagurus) ; the smaller star-fish ; and the tube- worm {&ur- 

 ]mlc£). In introducing fisli, care should be taken to select the most 

 amicable; a small shark, for instance, was once introduced into the 

 aquarium of the Emperor William, at his country-seat in Prussia. 

 The efiect was, that all the other fish forsook the tank, and fled in great 

 confusion into a fresh-water one adjoining, nor could they be driven 



