Phyllopod Crustacea. 333 



1st of August, I found eiglit of them jmrtly filled Avith water, 

 in six of which the Artemice were found in abundance, though 

 more numerous in one than in anj of the others. In one tub, 

 in which the water had a decidedly milky appearance, they 

 were so abundant that hundreds could be obtained in a few 

 minutes. The water in some of the other tubs containing them 

 was of a reddish or brownish hue, or about the colour of weak 

 tea. In two no Artemice could be seen ; and in these the water 

 appeared to have been more recently renewed. Search was 

 made in the pools from which the water had been taken ; but 

 no Artemice were found, though doubtless from these places 

 the progenitors of those inhabiting the tubs must have been 

 taken. It is probable that in the pools they exist in very 

 small numbers, being kept in check partly by various small 

 fishes and other enemies, and partly by the unfavourable cha- 

 racter of the water ; while in the tubs the density of the water 

 is more favourable for their rapid increase, and unfavourable 

 or fatal to their enemies*. The water from the tubs, when 

 examined with a high power of the microscojDC, was found to 

 be filled with immense numbers of Infusoria of various kinds, 

 such as Monads, Vibrios, and Bacteria, most of which were so 

 small as to be distinguishable only as moving points with a 

 ^-inch objective. 



In the salterns of France the Artemice are associated with 

 immense numbers of a monad, usually bright red in colour, 

 Avhich has been named Monas Dunalii by Joly, who attributes 

 to it the red colour which the brine assumes just before crys- 

 tallization f, as also the red colour observed in the ArtemicB^ 

 which doubtless feed upon it as well as upon various other 

 living Infusoria and dead animal and vegetable matter of va- 

 rious kinds J. The Monas Dunalii appears in abundance in 

 the water having the density most favourable for Artemia, but 

 increases in far greater proportion in the still denser, nearly or 

 quite saturated brine in which Artemia does not live. The 

 observations of Payen and Joly show that the A. salina of 

 France can exist in waters varying in density from 4° to 20° 

 Baume, but that they flourish best in those that have a density 

 of 10° to 15° §. According to Eackett, those of Lymington 



* The density of the water in two of the tubs containing most Artemice 

 was l-06o, equivalent to a brine containing 9-07 per cent, of salt. One of 

 those tested was brownish, the other milky. 



t " Recherches sur la Coloration en Rouge des Marais Salans Medi- 

 terran(5ens," par M. Joly (Ann. d. Sci. Nat. 1840, ser. 2. t. xiii. p. 266). 



X According to M. Joly {op. cit. p. 262), a beetle, Hyclroporus salinus, 

 Joly, also inhabits the salterns where the water has a density of 6° or 7° 

 Baume, and preys upon the Artemice. 



§ 4° to 20° Baume is equivalent to a density of about 1-02 to 1 16; 



