June, 1919] 



Fauna of Rock Bottom Ponds 



437 



The shallowest water offered a rather uncertain habitat, 

 since even a very slight lowering of the general water level 

 would lay the bottom bare, and, indeed, even without such an 

 occurrence, the depth of water was hardly sufficient to accom- 

 modate any but the smallest animals. 



The number of species found is the same as for Station 3 

 but the species differ. They are given in Table 4, page 438. 



No general counts were made. On the whole, however, 

 there were very few individuals of any one species. With the 

 reduction in the amount of algae, gyrinid beetles were again 

 present where the water was deep enough for their maneuvers. 





Station 4 of Pond I. 



In the precarious littoral zone there were few species and also 

 few individuals. In ten linear feet only five Physce. were observed 

 and only one hybrobatid, Gerris, was seen in twice that distance. 

 The scarcity of algas was one reason for the comparatively few 

 PhyscB. Here and there patches of filamentous algae were 

 present and near these spots Physce and also Hydroporus were 

 noticed. I observed two or three sandpipers running along the 

 water's edge. This bird was apparently quite a frequent visitor 

 since its footprints were numerous. 



Plankton. The plankton material taken in the summer of 

 1917 was accidentally destroyed. Material was again obtained 

 in July, 1918. Although this does not represent conditions as 



