230 BULLETIN OF THE UNITED STATES PISH COMMISSION. 



Duck Lake. As additional material for comparison, the results of a visit to Duck 

 Lake, close beside the West Bay of Yellowstone Lake, may be worthy of present men- 

 tion. This clear, cold lakelet, about half a mile long and three-fourths as broad, lies 

 in a steep, oval hollow of the woods, its shore without beach, too deep for vegeta.tiou, 

 and surrounded by a tangle of fallen trees a secluded woodland pool. The special 

 peculiarity of the little collection brought in from here August 4 consists in the pre- 

 dominance of Diaptomus lintoni (the only Diaptomus found) over the other entomos- 

 traca, and the vast abundance of a shelled infusorian (Difflugia glolnilosa) brought up 

 by the dredge at 65 feet and by the towing net sunk to a depth of about 30 feet. 



Alongshore a small but miscellaneous collection was made of dragon-fly larvae 

 (Libellulinw and Agrionina;), larval May flies and Chironomus, of several AmpMpoda 

 (mostly Allorchestcs dentata), of various entomostraca, among which were Simoceph- 

 alus vetulus, Cyclops gyrinus, and other species of Cyclops, Alona, etc., and of the 

 common large leech, Nephclis maculata. In the dredge, besides the Difflugia already 

 mentioned, were several specimens of cyprids (Candona), very many Chirononnis 

 larvae in their tubes, Cyclops minnilm (a few), a few Corethra larvae, Diaptomus -lin- 

 toni, and a small auguillulid worm. The water at some depth was loaded with small 

 pellets of uniform size and similar shape, made up of diatoms, fragments of filamentous 

 and other algaj (mostly emptied of chlorophyl), and of other vegetable debris together 

 with grains of sand, all of which had the appearance of being the excrement of the 

 common Ghironomm larva. So thick was this material that it soon lined the surface net 

 when hauled some 30 feet below the surface. With it came, besides Difflugia, a few each 

 of Corethra larvae, Daphnia pulex, Diaptomus lintoni (all females or young), and a single 

 Gammarns. A surface haul gave a substantially similar product, with the addition 

 of the entomostracan Sida crystallina, not recognized in the adjoining lake. 



Lake of the Woods. Here, as. well as anyhere, may be reported the product of a 

 very little work done with the dip net along the margins of a little oval pond a quarter 

 of a mile in length, lying among the hills above Obsidian Cliff, at a height about the 

 same as that of Yellowstone Lake. It has neither outlet nor inlet, and is doubtless 

 fed -by springs. It was evidently shallow, although it was not sounded by ns, its 

 bottom apparently fathomless mud, and the open water of its center bordered all 

 round by a belt 100 feet wide of pond lilies and the usual accompanying vegetation. 



Collections could only be made among the lily pads with a hand net from a log 

 near shore. They were remarkable only for the variety of entomostracan and insect 

 forms and the vast abundance of a Stentor which blackened the surface in patches 

 some inches across and covered the lower surfaces of the lily pads as if with a layer 

 of soot. This is allied to Stentor igneus, from which it differs, however, by characters 

 to be derived from the description published on page 256. The principal insects taken 

 were ephemerid and Chironomus larvae, a few caseworms, a specimen of the water- 

 beetle Oraphoderes fasciaticollis, many black spring-tails (Poduridw), and several 

 water-spiders. Sida crystaUina was the most abundant crustacean, but specimens 

 were also taken of Scapholeberis mucronatus, Cyclops, Diaptomus, Simocephalus vetulus, 

 and Acroperus leucocephalus. A few examples of Allorchestes dentatus were also seen, 

 aud a fragment of a hairy, bristled worm (Naidomorpha). 



