RECENT FRESHWATER INVESTIGATIONS 263 



emphasis is laid upon those groups which are plankton forms, 

 whereas others have received at most passing attention. There 

 is also a considerable amount of literature bearing upon the 

 technical phases of the subject, in its relation for instance to 

 the purity of a city water supply, which has been included so 

 far as references were found without any effort having been 

 made to cover the entire ground. 



It is in dealing with the field of plankton work that I have 

 endeavored to include every article, however small, and to add 

 references to such reviews as were noted in order to make 

 the contents of the original articles more widely useful. 

 In this I have been greatly aided by the admirable reviews of 

 Zschokke in the Zoologisches Centralblatt; more recently Ko- 

 f oid has undertaken similar abstracts in the American Naturalist. 

 No effort has been made however to distinguish here between 

 comments, reviews, and abstracts, or to include all such notices 

 in the bibliography. A slight delay in the printing of the 

 paper enables me to include references up to the close of 1898. 



In so extended a review the method of citation must neces- 

 sarily be brief yet such as to allow of the ready finding of 

 papers cited. I have adopted the following: — The name of 

 the author together with the year of publication of the article, 

 bearing a letter affixed if necessary, forms the designation of 

 the paper. The title of the article is not abbreviated, but 

 written precisely as given by the author. The name of the 

 journal is shortened as much as consistent with clearness and 

 three or four which are in constant use, are designated as 

 follows : 



B. C. Biologisches Centralblatt. 



J. R. M. S. Journal of the Royal Microscopical Society, 

 London. 



Z. A. Zoologischer Anzeiger. 



Z. C. Zoologisches Centralblatt. 

 The abbreviations vol., pt., p., etc., are entirely omitted 

 but the following arbitrary order of arrangement will enable 

 any reference to be read with ease. 



