OUTLINE OF STUDY. 7 



not follow absolutely this classification, yet they have a close 

 relation to it. 



Green lake may be considered the typical deep lake of Wis- 

 consin, and, as observations have been carried on upon its fauna 

 and flora for a number of years, it was natural to select it for 

 comparison with Lake Winnebago. 



Collections were made on as large a number of lakes in other 

 localities as time would permit. Some of these lakes were se- 

 lected because they had apparently different conditions from 

 those prevailing on Lake Winnebago and Green lake, but 

 others were taken for the express reason that their conditions 

 seemed to resemble very closely those of the lakes which were 

 made the standards of work. 



Inasmuch, as will be shown later, experience has shown that 

 plankton collections are really significant only as averages can 

 be obtained of a considerable number of collections, and that 

 single collections may be very misleading, so far as possible an 

 attempt was made to visit a certain number of lakes repeatedly, 

 rather than to make a large number of single collections from 

 different bodies of water. Unfortunately the time at command 

 did not permit of as many of these trips as was desirable, so 

 that in some cases single collections only could be made: as 

 it was important that there should be as wide a basis of com- 

 parison as possible, it seemed better to make these single 

 collections than no collections at all. The author clearly recog- 

 nizes, however, that it would have been much better had it 

 been possible to work a circuit of a considerable number of 

 lakes continuously. If lakes could be classified into a series 

 of a few types, of course, it would be necessary only to take one 

 of each type. But, so far, no entirely satisfactory classifica- 

 tion, from the standpoint of the fauna and flora, has been pro- 

 posed, so that one can not be certain when he limits his work to 

 a few lakes, that he may not miss some important principles of 

 distribution which are only exemplifkd in the bodies of water 

 which he has not examined. 



Four somewhat extended trips, in four successive years, were 

 made to lakes in the forest reoion of Wisconsin, includino- lakes 



