THE ORGANIZATION OF DAPIINIJ PULEX. (i) 

 By Thomas Tate, of Bradford, Yorks. 



The " water fleas " are sufficiently abundant to ensure their being 

 neglected by the bulk of observers. We are apt to prize and study 

 most what is rare, though the patient investigation of a common form 

 and its affinities may often result in more substantial gain. If the 

 reader can imagine a shrimp suspended by the head within the two 

 valves of a mussel shell, both — shrimp and shell — being as trans- 

 parent as glass, and of almost microscopic minuteness, he will have a 

 rough notion of the animal whose organization is the subject of this 

 paper. For the DapJinias belong to the Entomostracous group of 

 Crustaceans : entomodracon meaning an insect within a shell." If 

 you hold one up to the light you will see a dark speck on the fore- 

 head — its eye — and a dark streak lengthwise, and curving under — 

 the digestive track. Produced from each side of the head you will 

 note a powerful branched or arborescent organ, waving to and fro 

 incessantly. These are its lai-ge inferior antennae, or arms, by which 

 the animal propels itself through the water in short and sudden 

 bounds. Hence its vulgar name, " branched horned water flea," dis- 

 tinguishing it from the " four-horned water flea " {Cyclops). This 

 minute crustacean is to be met with in fresh-water ponds and ditches, 

 most abundantly in situations where the water is renewed from time 

 to time by an overflowing stream. Its office in the economy of 

 nature is that of a scavenger ; rapidly devouring, as it does, the 

 vegetable and animal particles floating around. It appears healthy 

 in captivity, but diminshes in size. 



Examined under a low power, one cannot fail to admire its 

 delicacy of structure, and the high vitality which it manifests. The 

 seeming complexity of its organization will disappear if we remember 

 that the two ends of its body are bent under the m.ain trunk. The 

 anterior extremity is curved downwards and backwards, the posterior 

 downwards and forwards. The chitinous exoskeleton is faintly 



N. S., Vol. i.— April, 1876. 



(1) Read before the Leeds Naturalists' Field Club and Scientific Association, 



Jan. 26, 1875. 



