4696 Crustacea. 



are novel, I have been induced to collect the results together, and 

 submit them to the readers of this Journal. 



The observations about to be detailed were made in the small tanks 

 or aquaria already described,* in which the balance between the ani- 

 mal and vegetable organisms in a medium of sea water was perma- 

 nently maintained without artificial aeration or disturbance. The 

 materials employed for effecting this, in the aquarium now under con- 

 sideration, consisted of the Ulva latissima and Enteromorpha as the 

 vegetable members of the circle; several varieties of Actinia, Madre- 

 pora, Annelida and Palaemon, to represent the animal section ; while 

 the functions of the scavengering mollusks were fulfilled by Littorina, 

 Trochus and Purpura. The small tank, containing these several 

 organized members, was constructed of a zinc framing 3 feet in length, 

 1 foot in depth and 1 foot in breadth, having the bottom, ends and 

 back filled with slate, and the front, or part towards the observer, 

 glazed with plate glass, the whole being covered over loosely by a 

 shade partially glazed, so as to impede the evaporation of the water, 

 exclude as much as possible the soot and dust of the London 

 atmosphere, while, at the same time, a continual change of air could 

 take place. A quantity of rock-work was also introduced, and so ar- 

 ranged that the creatures could readily find a retreat, or screen them- 

 selves from the strong influence of the sun's rays during the day, and 

 from the numbing effects of radiation in a clear night. A short and 

 small shingle beach was also constructed at one extremity of the 

 aquarium, to enable the various denizens to retreat to shallow water 

 whenever they should be so inclined. 



Into this vessel, thus arranged, several individuals of the common 

 prawn were introduced during the months of October and November, 

 1852 : they were fed every second or third day with small pieces of 

 either oyster, mussel, cockle, shrimp, and the like, or, when these could 

 not be obtained, with softened shreds of raw, lean meat, which had 

 been previously dried by exposure to the air, in order to preserve it 

 from putrefaction, and allow of its being kept as a store of provision 

 capable of being had recourse to as occasion might require. 



The manner in which these beautiful creatures take their food while 

 foraging about the tank is very interesting. The first and second pair 

 of didactylous feet are cautiously and continuously thrust into every 



* Transactions of tlie Chemical Society, as published in their ' Quarterly Journal,' 

 vol. iii. p. 62, 1850; 'Garden Companion,' January, 1852; 'Annals and Magazine 

 of Natural History,' vol. x. p. 273, and vol. xii. p. 319. 



