ECOLOGY OF ISLE. ROYALE. 19 



several inches below the water level with the weight of one's body ; occa- 

 sionally small but deep holes are found through this substratum, and 

 care must be taken to avoid them. This zone is very broad and contains 

 an abundance of life. Outside the sedge zone occur alders and Tama- 

 racks, which border the forests at the base of the slopes. 



The fauna of the open Waterlily, Bulrush and Potamogeton zone con- 

 sists of insects flying over the water, such as the dragonfly, Aescfma 

 and the leaf beetles Donacia, which abound, especially about the Yellow 

 Waterlilies. On the surface film were water striders, Gerris margitia- 

 tus, and whirligig beetles, Gyrinidae. Sticklebacks were abundant, and 

 are quite characteristic of such waters, as is another small fish. Loons 

 were . frequently seen here, and also a Hooded Merganser. ToAvard the 

 outer margin of this zone where the lilies are often closely matted on 

 the surface, the insect life and the surface film fauna are the most 

 abundant. A live mussel, Anodonta grandis fooUana, was found on the 

 bottom ; and the snails, Planorhis cam/panulatus and parvus, were found 

 in small pools in this sedge zone. The bottom in this vicinity, and that 

 bordering the water margin of the ridges, is covered with a mass of 

 partly floating debris, the appearance of which suggested to Wood, who 

 first observed it, that something had exploded and scattered the strands 

 of debris about the surface. It is not improbable that the formation 

 of marsh gases will adequatelv explain this phenomenon, (Of. Penhallow, 

 Science Vol. 22, 1905, pp. 794-796). 



The dragonflies were EnallagnM hageni, Aeschna, Somatochlora sJmrt- 

 leffi, and Lucorhina proxiiiw, the last being very abundant. 



Where the sedge zone was absent, as at our raft landing at the end of 

 the trail, an abundance of needles, leaves and twigs from the over- 

 haiuging conifers and hardwooOd had accumulated at the shore, and were 

 stained almost black. The water of the lake is brownish. At this 

 point a number of invertebrates were taken, including shells, leeches, 

 insects, etc. 



Station IT. Tohin Harbor and Vicinity. As very little time was 

 spent at this station, the description will be correspondingly brief. Tobin 

 Harbor is a deep, narrow, protected bay, similar to that at the head, of 

 Eock Harbor, but narrower. The adjacent hills are forest covered, 

 largely with Aspen and White Birch. In the vicinity of Neutson's Resort 

 there is a large, cleared area. Mattson's resort is located on an island in 

 this Harbor. The most marked scenic feature of the Island, Monument 

 Rock, is on the north side of Tobin Harbor. 



It is a noticeable fact that many of the low islands in Tobin Harbor, 

 and especially those near its eastern end, are clothed with vegetation 

 close to the edge of the water. They are thus in marked contrast with 

 the islands along the southern shore, and to the various points of rocks 

 which project into the water. 



Upon a small island. Number 14 on the Land Office map, were found 

 small rock beach pools, just above or near the height of the usual quiet 

 weather waves. The water in one was about a foot in depth and con- 

 tained a very small amount of algal growth. In this pool were found 

 water striders, Oerris remigis, a few other insects (No. 30), and small tad- 

 poles. In another small pool about 10 inches above lake level, and with a 

 temperature of 77° (the. Harbor water having a temperature at the 



