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 (Nuphar] in the net. These waters were 

 swarming with life, chiefly insect larvae and crustaceans. They apparently contained 

 relatively few inollusks, several specimens of a large Phym, a few Pisidium and one 

 Amnicola occurring in our collections. The insect larvie included Agrion, Ephemera, 

 Chironomus, Corisa, Hydrophilus, and Corethra. The only amphipod crustacean was 

 Allorchestes dentata, represented by but few examples, but the open water contained 

 a great quantity of Daplinia angulifera and an occasional Sida crystallina. Among 

 the lily pads the same Daplinia occurred, together with a great number of Sida, a few 

 examples of Cyclops and Diaptomi, and several of Vaphnella 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 eleyans 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 Hydrachnidw, 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 Unionidw, 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 crustaceaii list. Polyzoa also were extremely few. 



Heart Lake. 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 rhomboidal 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 which 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 



