THE PLANKTON OF SHAWNEE CAVE. 399 



would be able to maintain themselves in a permanent pool cut off 

 from the cave stream is conjectural, as no such pool exists in this 

 cave. 



Tha the algae could not live in the total darkness of the cave 

 is certain. The method was not adapted to the investigation of 

 the bacteria and the infusoria. 



Relation of the Cave Plankton to the Permanent Cave Fauna. 

 The plankton of this cave does not form nor can it become a 

 part of the permanent fauna of the cave, because the current of 

 the stream in its higher stages is powerful enough to carry out of 

 the cave all forms that are not strong swimmers, or have not de- 

 veloped the habit of living under rocks or on the bottom. Cceci- 

 dotea, Crangonyx and Cambarus live on the bottom and under 

 rocks. Ambylopsis is a fairly strong swimmer and when struck 

 by a current goes to the bottom or under a rock. These animals 

 are examples of forms whose habits prevent them from being 

 carried out of the cave. 



Banta has taken Cyclops from the stomach of Amblyopsis 

 spelceus. This suggests that the plankton is a source of food for 

 some of the permanent cave animals. 



The organisms of the cave plankton are essentially pond forms 

 and their presence in the cave is accidental. They do not migrate 

 into the cave to colonize it. 



Summary and Conclusions. I. The form of the cave is deter- 

 mined by the direction of the seams in the limestone, the obstruc- 

 tions, and a factor X, which is probably elevation. 



2. The form of the cave thus determined results in a large 

 amount of residual water in the cave. 



3. This residual water causes the extreme flood temperature to 

 occur twenty-four hours or more after the crest of the flood. It 

 also causes the rate at which the plankton is carried through the 

 cave to vary directly as the stream level varies. 



4. Water temperature varies much more than the air tempera- 

 ture in the interior of the cave. 



5. Air currents in this cave are caused by and their rate varies 

 directly with the divergence of terranean and subterranean tem- 

 perature. 



6. The amount of plankton in the cave is relatively small. 



