FRESH-WATER BIOLOGICAL STATIONS OF THE WORLD. 503 



tions into, first, individual resorts; second, periodic resorts, and third, 

 permanent stations. Individual resorts are sucli as are characterized 

 by the work of one or more individual investigators, working for the 

 most part independently, and solving their problems by virtue of their 

 individual investigations. There are, of course, a large number of such 

 places where some investigator has made sporadic or single efforts at 

 the determination of the faunal character of a water basin, or has paid 

 a number of occasional visits to such a locality for the same purpose. 

 On the whole, these stations have accomplished comparatively little, 

 although we find striking contradictions of the general statement. 



They may be, however, of a more regular and definite character, and 

 some of these personal investigations have been most valuable in 

 extending our present knowledge of fresh- water life. It may be noted 

 here that the permanence or regularity which contributes to the success 

 may be either in the location of the point at which the investigations 

 are carried out or in the definiteness of the purpose which is followed; 

 thus Imhof's studies on the pelagic fauna of the Swiss lakes were per- 

 manent in their value, and Zschokke's investigation of the biological 

 character of elevated lakes carried on at numerous points in the Alpine 

 chain has resulted in fundamentally important contributions to the 

 lacustrine fauna of high altitudes. Yet neither of these was at all con- 

 fined to a single locality, though limited by a definite purpose. 



Periodic resorts are those to which groups of individuals are accus- 

 tomed to go for a certain portion or season of the year, most commonly 

 for a vacation period, in accordance with which they are denominated 

 summer or winter laboratories. The larger number of the investigators 

 tends toward securing a more complete idea of the biological problem 

 as a whole, so that the results obtained from such stations are of evi- 

 dent value. Yet at the same time it must be noted that they are dis- 

 tinctly inferior even to many individual resorts, since during the larger 

 portion of the year no investigations are carried on and the results 

 obtained are necessarily partial and incomplete in their character, and 

 hence unavailable for the decision of the broader and more fundamental 

 biological questions. 



Permanent stations are those at which operations are conducted 

 throughout the entire year by a definite corps of observers. The con- 

 tinuity of their work renders their results valuable for the decision of 

 general biological problems, and at the same time the permanent force 

 which, in part at least, is indispensable in such an institution implies 

 that the undivided attention of the observer is devoted to these prob- 

 lems; from this we may then expect justly that greater results will be 

 obtained than in the case even of the best of individual resorts, since 

 the investigators who are carrying on operations at these are, so far as 

 I know, without exception connected with educational or scientific 

 institutions which demand at least a part of their time, and to that 

 extent divide their interest and their energy. 



