460 



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



In connection with the absence of surface feeding fishes it is 

 interesting to observe that the surface and pelagic insects such 

 as Notonecta, Corisa and Gyrinus were present. 



From the quantitative plankton table, Table 20, it will 

 be seen that the phytoplankton made up by far the greater 

 part of the entire plankton. The quantity of zooplankton was 

 not large. All members of the zooplankton composed an approx- 

 imately equal portion of it. Although Potamocypris was "the 

 least abundant of the plankton species, it was present in swarms 

 that covered large patches of the surface. This abundance was 

 merely a temporary matter since it is a species that is usually 

 most in evidence during a few weeks only, 



TABLE 20. 

 PLA^'KTO^ Quantitative Results. 



Species 



Closterium 



Potamocypris 



Cypris inequivalva . . 



Cypris sp 



Rotifera 



Ceratium lonpicorne. 

 Arcclla vulgaris 



Nltviber in 

 100 Liters 



535.750 

 5.000 

 5,890 

 6,250 

 5,750 

 5,250 

 5,375 



Per Cent. 

 OF Total 



94. 

 .878 

 1.03 

 1.09 

 1. 

 .09 

 .09 



THIRTY YEAR POND. 



Pond V. 



In the grounds of the Soldiers' Home at Sandusky there is a 

 group of three ponds supplied with water by a small stream from 

 nearby springs. The ponds are at different levels and water 

 passes successively from one to the other when there is enough 

 of it to cause an overflow. At times the lower pond overflows 

 and, by means of a ditch, connects with a creek about one-third 

 of a mile distant. In the source of the water and in the 

 occasional connection with the creek these ponds differ from 

 the others included in this survey. These conditions may sug- 

 gest that Pond V is not in a class with the others. The differ- 

 ences are not so vital, however, as they appear. The supplying 

 stream, because of its own isolation and short extent, can have 

 had little influence in introducing forms which would not 

 otherwise have reached the ponds. The connection with the 

 creek has been such an intermittent occurrence that any 

 possible migration along this route must have been precarious. 



