24 THE AQUARIAN NATURALIST. 



Actiniae; in a third, Corallines, Annelids, Polyps, 

 Rock-borers, Sabellse, Serpulse, Holothurise, Actinise, 

 and so forth classifying with care the occupants of 

 each tank according to their various habits. 



Temperature* is a point of great importance. The 

 mean temperature of the ocean is estimated to be 

 about 56 Fahr., and this under ordinary circum- 

 stances does not vary more than about 12 through- 

 out the different seasons of the year. 



Many of the inhabitants of the sea are very sensi- 

 tive to changes of temperature, and we find that a 

 few degrees of variation will cause them rapidly to 

 move their position, and seek some cooler or warmer 

 spot, as the case may be. In the ocean it will be 

 evident that the creatures have the power readily to 

 effect this, under ordinary circumstances, by seeking 

 deeper water, not liable to be affected by atmospheric 

 influences, by partially, or entirely, burying them- 

 selves in the sand or shingle, or by shielding their 

 bodies under the protecting shadow of the rocks, or 

 growing vegetation. In arranging the rock- work in 

 the interior of the aquarium, therefore, great care 

 should be taken to keep these points in view, and to 

 afford as much protection as possible to the creatures 

 from the cooling influences of radiation on the one 

 hand, and from the heat of the sun's rays upon the 

 other. " From my own experience," says Mr. Wa- 

 rington, " I find that the range of temperature should 

 not be below 50 Fahr., nor above 70. Within these 

 limits all appears to progress healthily ; but beyond 

 these points many of the creatures are rapidly affected. 

 * Warington, Ann. Nat. Hist. 1855. 



