304 henry b. ward: 



But few bibliographies bearing upon the subject of fresh- 

 water investigations have yet been published. That of Dolley 

 (96) is most largely marine, while those of Apstein (96) and 

 Field (98a) are exclusively confined to plankton studies. Others 

 treating of single genera or groups occur in systematic papers 

 on these forms. 



The work of Mez (98) is rather of a technical character for 

 use in water analysis and treats of Protozoa alone among ani- 

 mal forms, discussing particularly their relation to the quality 

 of the water and their dependence upon its physical and chem- 

 ical character. American students are awaiting eagerly a 

 somewhat similar work by Whipple, which is already an- 

 nounced. 



Stokes (96) is a convenient summary, largely taxonomic, of 

 freshwater genera: it contains, however, data on apparatus for 

 collecting and notes of a biological character. 



In the line of apparatus for special work on limnetic ques- 

 tions much has been done ami yet mostly in the direction of 

 adapting that used in marine investigations to the conditions 

 in fresh water. A recent ami comprehensive discussion of the 

 former may be found in Ilensen (95), whose assistant, Apstein, 

 was the first to apply the same methods to freshwater studies; 

 the latter has given (96) an extended account of the forms of 

 apparatus used in his plankton investigations and somewhat 

 generally applied by others also. Forel (92, 95) mentions 

 numerous pieces of apparatus used in physical, chemical and 

 metereological studies on Lake Geneva. Here also Ule (94). 

 Frie and Yavra's account (94) includes figures of many kinds 

 of smaller collecting appliances, and Klunziger (97) refers in a 

 general way to plankton apparatus. R. H. Ward (95) speaks 

 of the advantages of the Birge net, particularly in shore col- 

 lecting and among marsh plants. 



Of new physical apparatus, the thermophone invented by 

 Warren and Whipple (95, 95a; of. also Whipple, 95) is un- 

 doubtedly the best instrument yet devised for recording water 

 temperatures. See Linsbauer (95) for a method of determining 

 the amount of light at a given depth. 



