3Q6 WILL SCOTT. 



to develop. A few wind-blown eggs and cysts may be carried 

 into the cave and develop there, but I think it extremely doubtful. 

 The second type of simple sinks develops many organisms, 

 but they are not admitted to the cave stream. 



Temporal Distributions. - - The temporal distribution of the 

 plankton in this cave is puzzling and the causes of this distribu- 

 tion are so complex that their analysis is difficult. 



Although qualitative methods only were used during the fall 

 and winter, there was less plankton in early winter than in the 

 autumn. From this it was tentatively concluded that the main 

 outlines of the temporal distribution of the cave plankton coin- 

 cide with that of lakes and rivers in temperate latitudes, in having 

 spring and autumnal maxima, and summer and winter minima. 



After a rain of 4.71 inches which fell on February 13 and 14, 

 I was unable to detect any organisms in the catch. Possibly a 

 few were present and were overlooked because of the great 

 amount of silt. 



In March a series of quantitative collections was begun and 

 continued for six months. During this period, two maxima 

 occurred. One was on May 14, and the other was on August 

 13. These were maxima both in number of individuals and in 

 number of species. Each was preceded by a very heavy rain. 

 Between these maxima there were no rains sufficient to affect the 

 volume of the cave stream. The maximum of May was larger 

 than that of August (see Table II). 



The February flood was accompanied by a marked decrease, 

 but those of May and August were accompanied by a sudden 

 increase and followed by a gradual decrease. 



From these facts it is safe to conclude that excessive rainfall 

 influences the amount of plankton per gallon of water in the cave, 

 but not always in the same way. Excessive rainfall affects the 

 amount of plankton in three ways, (i) The pools in plankton 

 producing sinks of the land surface over the cave overflow and 

 the organisms contained in them are carried into the cave. (2) 

 The plankton is diluted in the sink where it is produced and is 

 further diluted in the cave by the water from sink-holes of the 

 first type. (3) The stream level is raised and the current is in- 

 creased This increase in the current causes many organisms to 



