22 THE AQUARIAN NATURALIST. 



production of those green slimy protophytes, with 

 which, without such interference, the glass sides of 

 the aquarium would speedily become coated over, 

 and the view of its contents, of course, proportionably 

 obscured. In the freshwater tank we find this im- 

 portant duty to be efficiently performed by a few 

 vegetable-eating Snails, and in sea-water it is fortu- 

 nately by no means difficult to avail ourselves of a 

 similar agency. The common Periwinkle, met with 

 abundantly on every rock, will be found most useful 

 for this purpose ; and if other vegetable-eating species 

 can be obtained of gayer colours, or more interesting 

 character, so much the better only let their number 

 be carefully adjusted to the work required to be per- 

 formed. 



All things being now in readiness, it but remains 

 to furnish the aquarium with appropriate occupants, 

 and in doing this, of course everything will depend 

 upon the opportunities or intentions of the proprietor. 

 Wide is the field, ample the store from which to 

 choose sometimes, indeed, too tempting. The great 

 danger is in overdoing this part of the arrangement, 

 in being too greedy for novelties a fatal error, which 

 surely brings its own punishment. It is difficult to 

 lay down any precise rule for the guidance of the 

 young aquariist experience will soon teach the juste 

 milieu, which must be strictly kept. It is much 

 better to have few specimens in the tank than one 

 too many. Should any specimens die, let them be 

 instantly removed ; and be careful not hastily to fill 

 up their places, unless quite sure that overcrowding is 

 not the cause of the mortality. A long glass tube, 



