AN ECOLOGICAL STUDY OF THE PLANKTON 

 OF SHAWNEE CAVE. 



WITH NOTES ON THE CAVE ENVIRONMENT. 1 



WILL SCOTT. 

 WITH THREE FIGURES. 



During the year beginning September 7, 1907, the speleological 

 fellowship of the department of zoology of Indiana University 

 was held by the writer with residence on the Cave Farm of the 

 University, three miles east of Mitchell, Ind. 



A preliminary examination of the cave stream revealed the 

 presence of considerable plankton. A systematic collection of 

 the plankton was immediately begun and after some time a 

 quantitative method applicable to the cave was developed. 



The organisms constituting the plankton were found to be 

 epigean forms. It developed that the seasonal distribution of the 

 cave plankton is different from that of epigean streams and lakes. 

 Its maxima and minima seemed more closely related to stream 

 level than to any other factor of the environment. 



These facts led to an examination of the surface of the region 

 overlying the cave, in order to determine if possible the source 

 of the plankton, and the relation of its source to its distribution 

 in the cave. It was found that the plankton is derived from 

 ponds in sink-holes of a particular type, and that its source is a 

 primary factor in determining its distribution. 



After the plankton enters the cave it is modified in various 

 ways by its new environment. The cave environment is divided 

 into two distinct regions, the terrestrial and the aquatic. These 

 two regions are alike in that there is an absence of light in both, 

 and that each influences the temperature of the other. They are 

 also both affected by the form of the cave. 



Some of their differences aside from their primary ones are : 

 (i) the temperature of the air approximates the temperature of 

 the walls of the cave very soon after entering it, while the tem- 



1 Contribution from the Zoological Laboratory of Indiana University, No. 104. 



386 



