June, 1919] Fauna of Rock Bottom Potids 463 



weeds. The physical conditions were everywhere so nearly 

 uniform and the distribution of the inhabitants was so general 

 that the pond has been treated as a unit. 



It will be seen by a glance at Table 21, page 462, that most of 

 the inhabitants, probably all of them except the fishes, are such 

 as could have entered by natural means even though there had 

 not been the partial connection with the creek. This connection 

 may have made it easier for the crayfish {Cambariis), the snails 

 (Planorbis and Physa), the leech {Glossiphonia) , the annelid 

 (Sparganophilus) and the planaria to have entered but all of 

 these are to be found in entirely isolated bodies of water so that 

 there is really no inhabitant, aside from the fishes, which would 

 probably not have been present under isolated conditions. 



The rich representation of insects is the outstanding feature, 

 but the animal characteristic of the pond is a fiatworm, Planaria 

 maculata. It was teeming over every submerged solid object. 

 I have never seen planaria so abundant anywhere. This condi- 

 tion was constant for the three summers over which my observa- 

 tions extended. The worms were about as numerous in the 

 middle pond but they were decidedly less so in the upper one. 



In connection with the insects it should be mentioned that 

 while a number of species are represented, the number of indi- 

 viduals in all but a few species is small. The presence of such 

 a variety of shore frequenting coleoptera is to be accounted for 

 by the debris about the edges of the pond which afforded a 

 suitable environment. Apparently the conditions were not 

 especially suitable for breeding since the absence of coleopterous 

 larvae was markedly noticeable. The species of insects which 

 were represented by numerous individuals all had larval stages- 

 in the pond also. 



The isopod, Aselliis attenuatus, was common everywhere, 

 but was not noticeably abundant. The same can be said 

 regarding the may-fly nymphs. Glossiphonia was more fre- 

 quently seen on the lower stones nearest the muck. 



The catfish and the carp are included on the authority of 

 persons living near the pond. I did not see either species 

 myself. The muddy nature of the bottom and the generally 

 congested conditions appeared to ofifer a more favorable environ- 

 ment for either of these fishes than for the sunfish. The presence 

 of surface feeding fishes is reflected by the almost total absence 

 of surface and pelagic insects. 



