June, 1919] 



Fauna of Rock Bottom Ponds 



431 



The water was blue with a tinge of green. It was sufficiently 

 transparent for the bottom to be seen anywhere. Its tem- 

 perature just beneath the surface was 28° C. In the deepest 

 water the bottom temperature was 26° C. In the shallower 

 regions there was no difference between surface and bottom 

 temperatures. 



Vegetation was confined to filamentous algae. These were 

 everywhere abundant and usually extended to the bottom. 

 Along most of the shore they were so thick as to form a dense 

 mat on the surface. Decaying algag were beginning to form 

 organic sediment on the ' bottom which as yet was scarcely 



Most of the One Year Pond is shown in this photograph. 



measurable. There was approximately a quarter of an inch of 

 inorganic sediment chiefly derived from the crushing of stone. 

 Most of the larger stones had been cleared away but there were 

 a few blocks at certain places. Details regarding these various 

 features will be given in connection with the data from each of 

 the stations. 



Station 1. This station covered a triangular bay enclosed 

 by a rock wall ten to twenty feet high which sheltered it from 

 all sides except the south. It is to be seen in the far corner of 

 the photograph on this page. The water was from six to eight 

 feet deep. Near shore, in shallow water, there were a few 

 millimeters of sediment. In the center there were in places 



