June, 1919] 



Fauna of Rock Bottom Ponds 



451 



The water was so turbid that the transparency disk disap- 

 peared two inches below the surface. This unusually low degree 

 of transparency was due in large part to the great quantity of 

 plankton, particularly the phytoplankton, which was so abun- 

 dant as to make the water green. Tests failed to show any 

 carbon dioxide either at the surface or at the bottom. The 

 temperature of the water was 29° C. just below the surface; 

 midway to the bottom and on the bottom it was 28° C. 



Station 1. The side of the pond at this point was a face of 

 solid rock similar to that shown in the left background of the 

 photograph on page 450. The water was two feet deep. A 

 miscellaneous assortment of stones was scattered over the 

 bottom. The forms found here were on these stones. A list 

 of them is given in Table 12. 



TABLE 12. 



The PhyscB were present down to the depth of a foot. The 

 beetle Hydroporus was taken in the algse along the water's edge. 

 The numbers given for the various individuals were taken at 

 random from several counts and represent average conditions. 

 The numbers for the may -fly nymphs and the chironomid larvae 

 indicate the average abundance of these species, on stones of the 

 size indicated, over the entire pond. 



Station 2. A pile of stones came to the surface at this 

 point. The situation is shown in the left half of the photograph 

 on page 450 just below the small bush. The animals found are 

 given in Table 13. Except for the beetles they were all taken 



