268 HISTORY OF BRITISH CRUSTACEA. 



assume a red colour, it has been said that they have com- 

 municated a bloody hue to water. Dr. Baird has observed 

 large patches of water of a ruddy hue, and ascertained the 

 cause to be an immense number of the Daphnia pulex ; 

 "the myriads necessary to produce this effect are 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 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 ob- 

 scure the sun, the whole body immediately disappears, 

 rising to the surface again when they have reached beyond 

 the shadow, or as soon as the cloud has passed over. They 

 are very prolific."* 



Subfamily Daphnina. 



Furnished with five pairs of feet j lower antennas two- 

 branched ; one branch divided into four, the other into 

 three joints. 



* Baird, Brit. Entomostraca, p. 78. 



