March, 1921] Afacro-Fatma of Mirror Lake 147 



Needham and Lloyd's ('16) classification of habitats of 

 ponds, satisfactory and sufficient at the same time for ecological 

 habitats and societies of animals is: (1) Littoral, or shoreward 

 area, with its divisions (a) Lenitic or Stillwater societies, and 

 (b) Lotic or rapid water societies; and (2) Limnetic, or open 

 water area, with its divisions (a) Plankton and (b) Necton, the 

 latter referring to the group of large free swimming animals. 

 Naturally no lotic area or conditions were present in the pond. 



The limnetic region in the large pond was extensive. A true 

 pond fauna, with insects, etc., as an important part would be 

 absent in a limnetic region. The necton, consisting here entirely 

 of fishes, was important, especially since the fishes were rather 

 too abundant and effective in reducing numbers among other 

 free swimming organisms. The plankton, which would be very 

 important, was not surveyed, except for such organisms as 

 ranged in the littoral zone. In the small pond there was no 

 true limnetic area at least not in its true sense, except when 

 the vegetation and especially the duckweed covering was not 

 developed early in the season. 



The littoral region, of prime importance in a typical pond, 

 was very much reduced in width in the large pond. While all 

 the stations here were in the littoral zone, as far as position is 

 concerned, results showed that stations 10, 8, 4, and to a smaller 

 extent, IB, 7, 6, and 5, (in about that order) were more or less 

 deprived of a fauna, except for a few surface forms (such as 

 water striders) which might, occasionally or frequently, be 

 there, and some possible bottom forms that may have been 

 missed. The shoreline in part at least, was not unsatisfactory, 

 and there might have been more evidence of the "sheltering 

 influence of shore," if there had been somewhat more vegetation, 

 and fewer fishes, which invade even to the shoreline. The broad 

 row of large, submerged stones along the north shore offered 

 good environment for lithophilous forms. 



In the smaller pond also the littoral region, included all 

 collecting stations, and included, when duckweed covered the 

 surface, practically the whole pond; or at any rate the pond 

 was more nearly of the littoral type than anything else. The 

 lack of emergent, rooted vegetation would not be tA^pically 

 littoral. The bottom mud was deep here, but no deeper than in 

 the large pond, and it had a larger deposit of humus. 



