230 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Duel: Lake. — As additional material for comparison, the results of a visit to Dunk 
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 vegetation, 
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- 
(lominance of Diaptomus lintoni ( the only Diaptomus found) over the other entomos- 
traca, and the vast abundance of a shelled infusorian ( Difflugia globulosa) 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 
( Libellulince and Agrionince ), larval May flies and Chironomus , of several Amphipoda 
(mostly Allorchestes dentata ), of various entomostraca, among which were Simoceph- 
alus vetulus, Cyclops gyrinus , and other species of Cyclops , A Iona , etc., and of the 
common large leech, Nephelis maculata. In the dredge, besides the Difflugia already 
mentioned, were several specimens of cyprids ( Candona ), very many Chironomus 
larvae in their tubes, Cyclops minnilus (a few), a few Coretlira larvae, Diaptomus din- 
toni, and a small anguillulid 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 algae (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 Chironomus 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 Coretlira larvae, Daphnia pulex, Diaptomus lintoni ( all females or young), and a single 
Gammarus. 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 Clift', 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 us, 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 epliemerid and Chironomus larv:e, a few caseworms, a specimen of the water- 
beetle Graphoderes fasciaticollis , many black spring-tails ( Poduridce ), and several 
water- spiders. Sida crystallina was the most abundant crustacean, but specimens 
were also taken of Scapholeberis mucronatus, Cyclops , Diaptomus , Simocephalus vetulus, 
and Acroperus leucoceplialus. A few examples of Allorchestes dentatus were also seen, 
and a fragment of a hairy, bristled worm ( Naidomorpha ). 
