372 MjTr U,WamgU)ii^Mt Notes on Jbfumah in tmall Aquaria, 



in a great degree forced i^Mm me firotii lerircnmstances wbich have 

 been already pfublished* In the paper read before the ^Meeting 

 of the British Awociation at Hull, 1 stated that in consequence of 

 the ravenous propensities of the crabs and the varieties of rock- 

 fish, I had been obliged to establish several small imitation rock- 

 pools, so as to separate these various depredators from each 

 other ; and as some of these, the blennies, also attacked the 

 common periwinkle and other mollusks which were employed as 

 scavengers, the plant or vegetation consequently became of little 

 use, and was therefore omitted altogether from the arrangement. 

 It may be asked then_, how can the sea water under such circum- 

 stances be possibly kept in a healthy state ? Why, thus : by ex- 

 posing a very extended surface of it to the action of the air, and 

 at the same time limiting its depth. The means that I have 

 been adopting for upwards of twelve months consist in the 

 employment of shallow circular stone-ware pans of about eighteen 

 inches internal diameter by iL\e inches deep ; these are filled for 

 about two inches with water, the bottom is supplied with sand and 

 shingle, and numerous fragments of rock-work are arranged at 

 the sides, some close below the surface of the water, others 

 rising in gentle slopes above, and others again grouped to form 

 cavities of retreat, so as to accord with the habits of the crabs, 

 blennies, &c. placed in them. The whole is covered with a sheet 

 of common window glass, raised about one-fourth of an inch 

 from the edges of the pan by means of slips of wood, so as to 

 allow a free current of air over the surface of the water, and at 

 the same time impede the evaporation and prevent the greater 

 part of the dust and soot from settling on it. By this arrange- 

 ment a very extended surface of water is submitted to the oxi- 

 dizing influence of the air, and the fish and crabs by their con- 

 tinual movements cause sufficient motion in the fluid to expose 

 a fresh surface frequently to its action and thus keep up its 

 aeration. But it must be borne in mind, that the oxygenation 

 of the water thus efiected is a very delicate equilibrium, and the 

 ^maintenance of a healthy aeration is Uable to be disturbed by 

 very slight interfering causes ; nor do I conceive that this method 

 would be applicable except to such marine denizens as are either 

 of such low organization as to require but little aeration of the 

 water, or to such as the crab tribe, the blennies, cotties, gobies, 

 and those creatures which delight in very shallow water, or 

 which have the power of climbing out of their liquid element. 

 The varieties I have myself kept in perfect health for the period 

 mentioned, are crabs, blennies, gobies, cotties, and varieties of 

 Actinia. Cancer Mcenas has under these circumstances cast its 

 skin three times during the present year, having increased in its 

 dimensions most extraordinarily each time. 



