THE MARINE AQUARIUM. 95 



along our shores, ami which belong to the genus Anomia, 

 make an excellent bottom. The)', of course, as well as 

 any other shells or pebbles that we intend to use as a 

 bottom, should be carefully washed — not for the purpose 

 of removing the salt, for that would do no harm in a 

 marine as it will in a fresh-water collection, but in order 

 to get rid of any decomposing animal or vegetable mat- 

 ter that might be adhering to them, and which would 

 foul the water ; and if we do not attend to this, wc shall 

 be apt to iutroducc sponges, zoophytes and alga?, dead 

 or dying, which would, of course, be dangerous inhabit- 

 ants. 



We must also remove all sponges and other minute 

 growths from pebbles, shells, rocks or other matters that 

 wc arc going to place in our tank, as they are all danger- 

 ous, being apt to die and decay before their demise is 

 discovered. 



Kockwork should be introduced sparingly into a marine 

 •tank ; but pieces of rock, bearing sea-weeds, can be piled 

 up in one comer with advantage, as it affords a point 

 — when projecting above the water — where such animals as 

 wish to do so can come out occasionally into the air. 

 The little fiddler crab (Gclasimas vocans) is one of these, 

 as we shall find if wc throw him into the water from his 

 native shore. On our doing so, he will immediately return 

 and attempt to find his burrow in the wet sand, and 

 even in a tank that has no rockwork projecting above the 

 surface of the water I have noticed this crab get upon 

 the highest point and lock upwards, as if wishing, wit!-. 

 an honorable ambition, to strive at greater things. If we 



