464 



The Ohio Journal of Science [Vol. XIX, No. 8, 



TABLE 22. 

 Plankton Quantitative Results. 



Species 



Bosmina lon^irostris 



Scapholebris sp 



Ophryoxus sp 



Ceriodaphnia sp . . . . 

 Potamocypris sp . . . . 



Nauplius 



Brachionus bakeri . . 



Ceratium 



Arcella 



Number in 

 100 Liters 



6.300 

 1,250 

 2,250 

 2,250 

 1.000 

 2.250 

 2,000 



Trace 



Few 



Per Cent. 

 OF Total 



36.4 

 7.2 



13. 



13. 

 5.7 



13. 



11. 



The plankton in this pond was predominantly zooplankton. 

 The quantitative results are given in Table 22. Bosmina 

 longirostris was the species present in the greatest abundance. 

 All the others were far less numerous. 



GENERAL DISCUSSION OF THE SERIES. 



Physical Features. 



A summary of the main physical features of the five ponds 

 has been arranged in Table 23, page 465. It will be seen that 

 there is a great difference in size between the largest and the 

 smallest; the two younger ponds are from five to ten 

 times larger than the three older ones. The latter are very 

 nearly of a size. In harmony with the size differences there is a 

 corresponding difference in temperatures; the larger bodies of 

 water are a degree cooler than the smaller. 



In a series of ponds such as we have here it is possible to 

 gain some idea of the rate at which sediment accumulates. 

 The amount of sediment which collects on the bottom of a 

 pond as it increases with age is a matter of far reaching import- 

 ance because of its influence on vegetation and on animal 

 inhabitants. The rate at which this accumulation takes place 

 is of value in determining the age of ponds whose past history 

 is unknown. 



The first of the two amounts indicating the depth of sediment 

 for each of the ponds in Table 23 is the more accurate record of 

 actual accumulation. The maximum depth of sediment in the 

 one year and the five year ponds was in an area where the 

 suction of a pump used in keeping the quarries dry had accu- 

 mulated considerable material from over a wide region. In all 



