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



This pond had the least number of species represented in its 

 population. In view of its age and also of the fact that it pre- 

 sented a less barren environment than the three younger ponds, 

 one could expect to find it inhabited with a greater variety of 

 species. The island situation is one of the first reasons to suggest 

 itself in explanation of this state of affairs. An examination of 

 Table 24 will show that for most groups this pond compared 

 favorably with the others in the number of species represented. 

 Its non-flying population such as annelida, mollusca, etc., was 

 about equal to that of the other ponds. In beetles it bore 

 comparison with the five and the ten year ponds. The greatest 

 loss in species came in the flying groups diptera, ephemeridae 

 and tricoptera. Isolation is hardly a satisfactory explanation 

 for loss in representation among these species. It seems more 

 probable that the condition of the water rendered the pond 

 uninhabitable for larval members of some of the groups found 

 in the other ponds. 



The thirty year pond presented several new species. Strange 

 as it may seem Planaria was found here for the first time. It 

 was by far the most abundant member of the association. 

 Crayfish also appeared here first and so did slugs and an annelid, 

 Sparganophiliis. This worm is to be found about the roots of 

 aquatic plants in marshes and older ponds, although I have 

 found it also along the pebbly and stony beach of a partly 

 protected bay on Lake Erie. 



The slugs, Liniax and Pallifera, were both in moist situations 

 under debris along the water's edge. The moisture and shade 

 afforded them by the grass and trees in the surroundings would 

 enable them to reach this situation without undue exposure to 

 dry conditions. The only other pond with approximately similar 

 surroundings was the one fifteen years old. All the others were 

 bordered by a greater or less expanse of bare rock which pre- 

 sented desert conditions to any animal that would have 

 attempted to migrate across it by crawling or creeping. In this 

 respect the one, five and ten year ponds had an additional 

 degree of isolation which undoubtedly prevented certain types 

 of animals from reaching them. Until this bare expanse of 

 rock is covered by vegetation it will continue to act as a barrier 

 and thus aid in keeping the associations of the ponds in an 

 ecologically younger condition. 



