454 Entomostraca {Water-Fleas). 



position, and in a very short time wheel completely round the 

 pond. Should the mass come near enough the edge to allow 

 the shadow of the observer to fall upon them, or should a dark 

 cloud suddenly obscure the sun, the whole body immediately 

 disappear, rising to the surface again when they have reached 

 beyond the shadow, or as soon as the cloud has passed over." 

 I on one occasion gathered a curious species, Cyjprideis torosa, 

 Rupert Jones (fig. 8), in such numbers, that when the contents 

 of the net were turned out into a bottle of water they resembled 

 a huge mass of mites in constant motion. Though naturally 

 unable to swim, they were literally "all alive and kicking; 

 this was in a salt marsh on the Northumberland coast, but it 

 is in the sea that Entomostraca reach their most astonishing 

 development as to numbers. So numerous are they in the 

 South Atlantic, that they form the chief food of the whale ; 

 and the red streaks which have been noticed as sometimes 

 occurring in freshwater ponds, may in those regions be seen 

 in the sea on an infinitely larger scale, stretching over many 

 miles of its surface. " They swarmed in myriads/'' says Vau- 

 zeme, " and when the wind was boisterous, a .whole bank of 

 them would be taken up by a wave, and carried on board the 

 vessel, covering the deck and the clothes of the sailors." On 

 our own coasts they may be seen in scarcely inferior numbers. 

 The Rev. Mr. Norman has noticed them in a sheltered bay 

 among the Shetland Islands, so numerous that the water was 

 literally thick — viscid with them, so that when a net was dipped 

 amongst them, and allowed to drain, quite a consistent mass 

 remained. And Mr. Goodsir says, respecting the Firth of 

 Forth : — " On looking into the water it was found to be quite 

 obscured by the moving masses of Entomostraca, which rendered 

 it impossible to see anything even a few inches below the sur- 

 face ; but if a clear spot is obtained, so as to allow the observer 

 to get a view of the bottom, immense shoals of cod-fish are 

 seen swimming lazily about, and devouring their minute prey 

 in great quantities. Occasionally small shoals of herring are 

 seen pursuing them with greater agility. Great numbers of 

 Cetacea often frequent the neighbourhood in the summer 

 months, droves of dolphins and porpoises swimming about 

 with great activity ; and occasionally an immense rorqual may 

 be seen, raising his enormous back at intervals from the water, 

 and is to be observed coursing round and round the island." 



As to diet, Entomostraca exhibit by no means a vegetarian 

 tendency ; on the contrary, they appear to be in many cases 

 most ferocious in their mode of supplying the commissariat. 

 Doubtless they fulfil a very useful purpose in destroying great 

 quantities of decaying animal mailer, and when put into an 

 aquarium which does not ati'ord a sufficient supply of this sort 



