Entcmostraca {Water-Fleas). 453 



lias been ascertained by M. Joly to depend on its food, which 

 consists to a great extent of a small rnonad (Monas Duvallii) 

 which colours the marshes and reservoirs of Montpellier. 

 Whether the same canse exists in the saltpans at Lymington 

 I do not know, but it is remarkable that the spontaneous vege- 

 tation which arises in vessels of stagnant salt water has often a 

 red hue. Thus, Mr. Gosse tells us* that a tank of sea water 

 on one occasion produced in great profusion patches of a " rich 

 crimson-purple colour," which spread rapidly over the bottom 

 and sides of the vessel, as well as over the surface of the water. 

 This proved to be a sea-weed of the genus Oscillator ia, appa- 

 rently undescribed in Dr. Harvey's Phycologia. But it seems 

 unnecessary to resort to phenomena of this kind for an explana- 

 tion of the colour of the Art&mia. There is a very common 

 tendency to redness amongst Bntomostraca, which appears to 

 be quite independent of the colour of their food. I have seen 

 a variety of Cyclops quadricomis so red as to appear like 

 brilliant spots amongst the mud in which it was taken ; and 

 amongst a gathering from Grisedale Tarn, in Westmoreland, 

 were multitudes of Diaptomus Castor, which looked like ani- 

 mated scraps of red sealing-wax. The marine species (Ceto- 

 chilus septentrionalis , &c.) may sometimes on a line summer 

 day be taken in such abundance as to resemble a mass of red 

 paint in the bottom of the net. The Great Salt Lake of the 

 Mormons is stated to contain twenty per cent, of saline con- 

 stituents — precisely the strength of the solution which Artemia 

 inhabits — and is also said to be quite devoid of animal life. We 

 do not read, however, that it has ever been examined with a 

 view to the discovery of minute forms. Possibly it may contain 

 curious examples of this much-enduring race, for that its waters 

 are not fatal to all phases of animal existence is proved by the 

 multitudes of caddis-cases which are found washed up on its 

 banks. 



Bearing in mind the excessive fecundity of Bntomostraca, 

 we need feel no surprise at the prodigious shoals in which they 

 are met with. Some of the Daplinice have been observed in 

 numbers large enough to give to the water in which they swam 

 the appearance of blood. Dr. Baird says that he has himself 

 seen " large patches of water assume a ruddy hue, like the red 

 rust of iron, or as if blood had been mixed with it, and ascer- 

 tained the cause to be an immense number of D. pulex. The 

 myriads necessary to produce this effect is really astonishing, 

 and it is extremely interesting to watch their motions. On a 

 sunshiny day, in a large pond, a streak of red, a foot broad, 

 and ten or twelve yards in length, will suddenly appear in a 

 particular spot, and this belt may be seen rapidly changing its 

 * Gosse's Romance of Nat. Hist. 2nd Series, p. 105. 

 VOL. I. — KO. VI. H H 



