220 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
From the swampy tract on the eastern side of the lake already mentioned col- 
lections were made by hauling a surface net in the open water, by searching dead 
leaves, and by washing off the lily pads ( Huphar ) in the net. These waters were 
swarming with life, chiefly insect larvae and crustaceans. They apparently contained 
relatively few mollusks, several specimens of a large Physa , a few Pisidium and one 
Amnicola occurring in our collections. The insect larvae included Agrion, Ephemera , 
Chiro nomas, Corisa , Hydrophilas , and Corethra. The only amphipod crustacean was 
Allorchestes dentata , represented by but few examples, but the open water contained 
a great quantity of Daphnia angulifera and an occasional Sida crystallina. Among 
the lily pads the same Daphnia occurred, together with a great number of Sida, a few 
examples of Cyclops and Diaptomi , and several of Daphnella and of Polyphemus pedic- 
ulus (young and adult), and a single short, dark cyprid. Leeches and their capsules 
were frequent, the usual spotted and striate species {Nephelis maculata and N. 4-striata). 
A single specimen of Clepsine elegans and another Clepsine not determined were also 
noticed. The capsules of these leeches were common on the leaves of water-plants. 
Among less conspicuous objects, small Hydrachnidce , Hydra fusca, and the colonial 
rotifer Conochilus were abundant. 
If we may pause now to glance at the animal life of these three lakes, character- 
istic as they are for their region, as compared with that of similar lakes of much lower 
altitude — Lake Geneva, in Wisconsin, for example — we find that the large and con- 
spicuous differences, so far as invertebrates are concerned, lie mostly in mollusks and 
crustaceans. The complete absence of Unionidce, of Paludinidce , Melaniidce , and of 
Valvata , and the scarcity of Planorbis and Amnicola are cases in point. The absence 
of crayfishes, of Epischura , and of Simocephalus is the most notable distinction in 
the crustacean list. Polyzoa also were extremely few. 
Heart Lahe. — Heart Lake had to us the very especial interest that it gave an 
opportunity, hitherto unparalleled in this country, to study by comparison the effect 
of the presence of fishes on the bionomic system of a mountain lake; and as the barren 
waters of Lewis and Shoshone lakes have since been stocked with trout by the U. S. 
Fish Commission, the results of this comparison of native conditions may hereafter be 
checked and supplemented by a study of the later state of invertebrate life in these 
two lakes. This lake is situated similarly to Lewis and Shoshone, is of nearly the 
same size as Lewis Lake, and is in most respects a companion to that and Shoshone, 
but differs totally in the fact that its outlet is unobstructed by falls and that it is 
consequently well supplied with fishes. It lies only 5^ miles from Lewis Lake, in a 
straight line, and about 6 miles from the southern arm of Yellowstone Lake, but the 
latter is on the opposite side of the divide and is consequently connected with a 
different system of waters. It is divided by a peninsula into two unequal parts, the 
larger of which, rudely rkomboidal in shape, is approximately 1.] by 2 miles in diameter. 
The smaller part is subtriangular, with principal diameters of about a mile, and the 
narrow neck uniting these two divisions of the lake is about a quarter of a mile across. 
Heart Lake differs from Lewis and Shoshone by its closer proximity to the Red 
Mountains, especially to Mount Sheridan, and consequently by the much greater 
amount of snow water whicli it receives. At the time of our visit, during the last 
days of July, the rush of rivulets down the mountain slope, supplied by the melting 
snows, filled the air all day with a noise like. that of a train of cars. This lake has 
also its hot-spring and geyser basin, but receives through Witch Creek a relatively 
