323 Mr. R. Wai'ington on Presej'ving the Balance between 



ing and devouring each other, and it therefore becomes a point 

 of great importance — and highly necessary to be carefully ob- 

 served, where their preservation is an object — to ascertain what 

 varieties may be safely associated in the same tank ; as, for in- 

 stance, I have found that the Shrimps and Prawns attack, and 

 verj' soon devour, all the larger varieties of Corallines and Polyps, 

 Sabellse, Serpulse, Rock-borers, Cirrhipeds, some of the Annelids, 

 many Bivalve and Univalve MoUusks that are unprotected by an 

 operculum, or have no power of closing their valves. The in- 

 stances which have come under my own immediate observation 

 have been the destruction of the Pholas dactylus, Saxicava rugosa, 

 Cyprcea Europcea, and several specimens of Sabellse, Serpulse, 

 Corijne sessilis and many others. 



Tlie common Crab {Cancer Mcenas) is likewise a most de- 

 structive agent ; and the tribe of rock-fish, the Bleunies, Gobies, 

 &c. are also most voracious, devouring all the varieties of Cirrhi- 

 peds, 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 

 tirm hold of the rock or tank sides, they are rapidly turned over 

 by these fish on their backs and lie helplessly exposed to their 

 attacks*. It is doubtless their seeking food of this kind which 

 causes these little fish to be so generally found in the shallow 

 iX)ck-pools of the coast. In consequence of these ravenous pro- 

 pensities I have been obliged to establish several small tanks and 

 imitation rock-pools, so as to separate these various depredators 

 from each other : thus in one I have varieties of Actinia, Shrimps, 

 Nudibranchs, Holothurias, and some Annelids ; in a second the 

 rock-fish, as the Bleunies, Gobies, Cottus, with Crabs and 

 Actinia ; in a third Corallines, Annelids, Polyps, Rock-borers, 

 Sabellae, Serpulse, Holothurias, and Actinia. 



Another curious instance of loss I may detail which has quite 

 recently occui-red, and which may prove interesting ; it was in a 

 small rock-pool containing Blennies, Gobies, Crabs, &c. I had 

 procured two live oysters for the purpose of feeding my nume- 

 rous small fry in these vivaria, and one of these having proved 

 ample for the purpose of one meal, the other was placed on the 



* Since the reading of this paper at Hull I have received a Blenny of 

 larger size, being about 85 inches in length, and although it has become so 

 tame that it will allow itself to be touched by the hand and takes its food 

 from the fingers, yet its destructive propensities are so great, that it very 

 soon killed four small Crabs ; and to save three others, of rather a larger 

 size, I have been obliged to remove the Blenny to a rock-pool in asso- 

 ciation with his own s])ecies and a few Actinia. The only refuge the poor 

 Crabs had was to bury themselves in the sand, and whenever they attem]ited 

 to move out of their refuge they were immediately potmced upon an<I only 

 escaped by burrowing rapidly again. 



