ASSORTMENT OF SPECIMENS. 23 



or a pair of forceps, with which the bottom of the 

 tank can be easily reached, should always be at hand 

 wherewith to take away whatever dies, and thereby 

 save the rest. 



Another source of loss arises from the creatures 

 attacking and devouring each other, and it therefore 

 becomes a point of great importance, and highly 

 necessary to be carefully observed where their pre- 

 servation is an object, to ascertain what varieties may 

 be safely associated in the same tank. Shrimps and 

 Prawns attack and very soon devour all the larger 

 varieties of Corallines and Polyps, Sabellse, Serpulse, 

 Rock-borers, Cirrhipeds, and some of the Annelids, 

 as well as many Bivalve and Univalve Mollusks that 

 are unprotected by an operculum, or have no power 

 of closing their valves. 



The common Crab (Cancer M&nas) is a most de- 

 structive fellow, and the tribe of Rock-fish, the 

 Blennies, Gobies, &c., are also awfully voracious, de- 

 vouring all the varieties of Cirrhipeds, Corallines, 

 Polyps, Annelids, &c. ; they will also attack the 

 Shrimps and Prawns, and even seize upon the horns 

 of the Periwinkle, which they bite. If the Mollusks 

 do not keep a very firm hold of the rock or tank-sides, 

 they are rapidly turned over on their backs by these 

 fish, and lie helplessly exposed to their attacks. It 

 becomes necessary, therefore, in consequence of such 

 ravenous propensities, to separate these various de- 

 predators from each other ; and in one tank to place 

 varieties of Actinise, Shrimps, Nudibranchs, Holo- 

 thuriae and Annelidans ; in a second, the Rock-fish, 

 such as Blennies, Gobies, Cotties, &c., with Crabs and 



