FEESH-WATEE CEUSTACEANS. 295 



There is, however, one other Entomostracon, which I think 

 ought, though rather rare, to be mentioned here, owing to its 

 beauty, viz., the Fairj Shrimp (Chirocephalus stagnalis). It 

 is about lin. long, and nearly transparent. The tail is a bright 

 red, and the back of the female is blue. It is found in 

 stagnant water, and, according to Dr. Baird, in ditches and 

 deep cart-ruts on the edges of woods and plantations. I 

 believe that it is nearly always to be seen in a pond on 

 Blackheath. Dr. Baird, in writing of the Fairy Shrimps, 

 says that "they swim upon their backs, and in fine warm 

 weather, when the sun is not too strong, they may be seen 

 balancing themselves, as it were, near the surface by means 

 of their branchial feet, which are in constant motion. On 

 the least disturbance, however, they strike the water rapidly 

 with their tail from right to left, dart away like a fish, 

 and hasten to conceal themselves by diving into the soft 

 mud, or amongst the weeds at the bottom of the pool. It 

 is certainly the most beautiful and elegant of all the Bnto- 

 mostraca. The male is especially beautiful: the uninterrupted 

 undnlatory, waving motion of its graceful branchial feet, 

 sUghtly tinged as they are with a light reddish hue, the 

 brilliant mixture of transparent bluish-green and bright red 

 of its prehensile antennae, and its bright ' red tail, with the 

 beautifully plumose setae springing from it, render it really 

 exceedingly attractive to the view. The undiilatory motion 

 of its branchial feet sei-ves another purpose in addition to 

 that of keeping the animal suspended in the water. The 

 thorax, or body, of the animal has been described, when 

 floating on its back, as like the cavity of a little boat, the 

 feet representing oars. When these are in motion, they cause 

 the water contained in this cavity to be compressed, and to 

 mount up as along a canal, carrying in the current the 

 particles destined for its food towards its mouth. It seems 

 to be constantly, when in this position, employed in swallowing 

 and digesting its food, its masticatory organs being in 

 perpetual motion.'' 



The food of this beautiful little crustacean consists of 

 animal and vegetable matter — chiefly, however, the former. 



