March, 1921] Macro-Fauna of Mirror Lake 149 



Phylum ANNELIDA. 



Subclass Oligoch.eta. 



Order Microdrili. 



Some worms of this group are among the most abundant 

 animals in the entire pond. They could be compared favorably 

 with midge larvae, but since a good habitat which no doubt 

 harbored myriads of some members of both groups, namely the 

 bottom mud of the large pond, was hardly touched, no real 

 estimate of relative numbers could be formed. The almost 

 total absence in the large pond as compared with the small, of 

 the mud-dwelling forms (Tubificidas) , is thus explained. Forms 

 dwelling where algas and other vegetation abounds, (Naididce) 

 would of course not be expected from most of the large pond. 



Family Naididce. 



Chastogaster sp. This was among the scarcer forms of this 

 family. The species could not be determined because of the 

 immature condition of the specimens. 



Slavina appendiculata (d'Udekem) (?). Worms of this genus, 

 which were more numerous than the foregoing, could not be 

 positively identified to species. 



Nais sp. These tiny, transparent worms were the most 

 abundant of the family. The largest number was found in the 

 very shallow water of station 11, and chiefly in late spring. 

 None were mature enough for specific determination. 



Dero limosa Leidy. While it is very likely this species, only 

 living material, (which was not available when Prof. Smith 

 named them), would make determination positive in this 

 genus. With a very few exceptions none of the specimens 

 secured had the characteristic case built by Dero. 



Family Tubificidce. 

 Limnodrilus sp. This was one of the most abundant animal 

 forms in the entire pond. Though not quite as many specimens 

 were collected as of Nais, it must be remembered that only a 

 very small part of its habitat was touched. They were quite 

 evenly distributed throughout the collecting period. None 

 were mature enough for accurate specific determination. Pos- 

 sibly all belonged to one species, which is at least very closely 

 similar to Limnodrilus Jwffmeisteri Claparede, found in Europe 

 and also in this country. 



