102 THE ZOOLOGIST. 



priate to aquatic creatures should once more revisit their thirsty 

 and solidified home. 



Of the three orders — Branchiopoda, Ostracoda, and Copepoda 

 — into which the Entomostraca are commonly divided, the present 

 paper touches only the first, and that in two of its divisions — the 

 " leaf-limbed " Phyllopoda, and Cladocera, with conspicuously 

 " branched antennae." The former especially excite surprise, 

 when they are successfully grown from dried mud, because of 

 their superior magnitude. Some of them also are remarkable 

 for having no carapace, others for being almost entirely enclosed 

 in what looks like the shell of a bivalved mollusc. The Clado- 

 cera are closely related to the Phyllopoda, and are most widely 

 known through the little Water-Flea (Daphnia pulex), which, 

 though little, is much larger than the Chydorus sphcericus, to be 

 presently mentioned. The labours of G. O. Sars in Norway, of 

 W. Lilljeborg in Sweden, of Jules Richard in France, of G. S. 

 Brady, D. J. Scourfield, and Thomas Scott in Great Britain, 

 and, in truth, of quite a multitude of learned writers all over the 

 world, have discussed almost every conceivable detail in the 

 structure, habits, and distribution of these animals. Even as to 

 their classification, a very near approach to agreement has been 

 arrived at. All the more desirable is it that every source of con- 

 fusion should, if possible, be eliminated from the names in com- 

 mon use. But in regard to the genus and family which form the 

 subject of this paper, there is something a little parallel to " the 

 strange case of Dr. Jekyll and Mr. Hyde." It is the object of 

 the following discussion to unmask them, in the sense of showing 

 what are the animals to which the designations that form the 

 title of this paper should rightfully be applied. 



It is said of mud that, if you throw plenty, some of it is sure 

 to stick. With scientific names there is an understanding that, 

 if they are thrown according to the rules of the game, they ought 

 to stick at least to some of the objects at which they have been 

 thrown. In early attempts at classification a generic name is 

 often attached to an incoherent miscellany of species. When 

 these are subsequently assorted under appropriate headings, the 

 original generic titles do not always quite know where they are. 

 They stand a chance of being left out in the cold, as things no 

 longer wanted — a kind of disinherited vagrants, blissfully for- 



