440 



UNSOLVED PKOBLEJrS. 



This study, while it gives ;i faivly eompleto picture of a particulni- 

 poud aud establishes some geueial notions concerning- ponds of this type, 

 is to be regarded as opening up a new corner in the field of freshwater 

 biology, rather than exhausting any part of it. The fauna of solution ponds 

 needs to be more carefully and generally explored. The life history of 

 many of the species Is quite unknown. Experimental studies on the effects 

 of varied conditions upon some of the organisms are certain to yield re- 

 sults. The details of the mode of dispersal are very imperfectly known 

 in many forms. 



The most Important general investigation, it seems, is to carefully 

 select a series of ponds having different combinations of environmental 

 factors, i. e., area, depth, shade, plant growth, wash, etc., and to make a 

 series of sinuiltaueous observations extending over at least one year. Then 

 by a process of elimination, determine the effect of these factors. 



I desire to express mj- oblig;itions to Prof. C. IT. Eyenmann aud Prof. 

 Charles Zeleny for their valuable suggestions aud criticisms. 



BIBLIOGRAPHY. 



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13, pp. 219-28. 



