INTRODUCTION. 3 



memoir, the arranging them into distinct genera, many 

 important and exceedingly interesting details regard- 

 ing them never before made known, and the addition 

 of a great number of new species which that zealous 

 naturalist discovered in the fresh waters and on the sea 

 coast of Denmark and Norway. He may be called the 

 first regular historian of these animals. To him it is we 

 owe a great deal of our knowledge respecting them, and 

 to his eloquent descriptions is perhaps owing the fm-ther 

 researches and more detailed histories of succeeding writers. 

 His work on the Entomostraca, published in 1785,* 

 though it contains several errors which have been pointed 

 out by later writers, is still one of the most interesting 

 memoirs in natural history that we are acquainted with. 



Since the time of Miiller much has been done by our 

 continental neighbours to add to our knowledge of these 

 interesting little creatures, and their individual labours 

 we shall take particular notice of as w^e proceed with this 

 work. It is cmious, however, that scarcely any British 

 naturalist, with the exception of Dr. Leach, has paid the 

 least attention to the Entomostraca. His memoirs are 

 scattered over a variety of publications, and a great por- 

 tion of his attention was directed to the history of the 

 parasitic animals belonging to the group. It surely is 

 not from want of interest belonging to them, that the 

 naturahsts of this country have so neglected these cmious 

 little animals, for many of them are worthy of all admira- 

 tion. "The multifarious and complicated structure of 

 their body," says Miiller, in his admirable work; "the 

 wonderful agility of their members ; the very great fine- 

 ness of their organs ; their singular method of living, and 

 copulating ; their living in waters which om- cattle and we 

 om'selves are daily drinking ; the evils which they may 

 give rise to, and which are seen to be inflicted upon 

 fishes; the advantages, although we are in the greater 



* Entomostraca, sen insecta testacca, quae iu aquis Daiiioe ct Norvcgia3 

 reperit, descripsit, et Iconibus illustravit Otho Fredericus Miiller. Lipsise 

 et Haviiise, 1785. 



