June, 1919] 



Fauna of Rock Bottom Ponds 



445 



Station 4. The fourth station covered an area representing 

 conditions in the central region of the pond, beginning at least 

 fifty feet from shore. The particular section studied in detail was 

 about one hundred feet off shore, midway between Stations 

 1 and 3. Its location is shown approximately by the position of 

 the boat in the photograph on page 448. About one-fourth of 

 the entire bottom in this region was covered by a rather thick 

 growth of Chara which grew in a substratum of mud formed 

 from quarry dust. The maximum thickness of this mud was 



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Station 3 of Pond II. 



three to four inches. The bottom over the rest of the pond 

 had a fine, silty deposit one-fourth to one-half inch thick and 

 was without vegetation. 



The animals taken from the bottom were about the same as 

 those in the bottom sediment of Station 1. A list of them is 

 given in Table 9, page 446. Here again the nematodes were 

 numerous. Blood worms were quite abundant. Larvae of the 

 midge, Corethra, were also found. Nats was more common than 

 at Station 1. An occasional Difflugia corona was observed. 



Fish were numerous all over the pond except in the shallow 

 pools of Station 2 and in most of the area covered by Station 3, 

 which was also shallow. From persons acquainted with the 

 history of the pond I learned that some fish were introduced 



