THE FRESH-WATER AQUARIUM. 81 



they were no more scavengers than the fish, we would 

 still introduce them into our collection, because of their 

 strange forms and habits. 



The little Craw-fish, or fresh-water Lobster (Astacus Bar- 

 tonii), is a curious creature, and resembles the common lob- 

 ster in everything but dimensions, as it is rarely over three 

 inches in length. It is said to be exceedingly common in 

 the mountain streams of this and the adjoining States. It 

 is shy in daylight, concealing itself under stones until night, 

 when it comes out. The American craw-fish is rarely eaten, 

 whilst the English species, A. Jluviatilis, is considered a deli- 

 cacy, and sold in considerable quantities in the London mar- 

 kets. Dr. Lankester mentions that he has never been able to 

 keep it alive in confinement, whilst Dr. Ball, of Dublin, kept 

 one so for two years. I have never myself tried to keep 

 tkcin, but suppose, with a little care, it may be accomplished. 



The fresh-water Shrimp {Gammarus minus), is common 

 in most of our fresh-water streams, and may be found by 

 searching under stones and pieces of wood. It is extremely 

 active, and if it could be kept alive, would make an in- 

 teresting inhabitant of an Aquarium. It is small in size, 

 being about one-third of an inch long, and resembles the 

 little sand-flea that we find under stones on the sea-shore. 



There is a small creature, the Asellus communis, that is 

 found in nearly every stream and often brought up in 

 great quantities by dragging the net along the bottom. 

 It looks somewhat like a larva of some insect, and is 

 extremely lively. I have found it easy to keep in an 

 Aquarium, although it is small, being only from a quarter 

 to a half of an inch in length. 



