. Animal communities in temperate America : as illustrated in the Chicago region; a study in animal ecology. Animal ecology; Zoology -- Illinois Chicago. EFFECTS OF DROUGHTS AND FLOODS 107 the headwaters at the rate of at least a mile per year, if they were intro- duced into a large stream. This must be a response to both water pressure and current. The small value of such single observations is recognized but they are presented here because the opportunity to secure such data is small. In this river there are also notable relations between especially dry seasons and the distribution of other
. Animal communities in temperate America : as illustrated in the Chicago region; a study in animal ecology. Animal ecology; Zoology -- Illinois Chicago. EFFECTS OF DROUGHTS AND FLOODS 107 the headwaters at the rate of at least a mile per year, if they were intro- duced into a large stream. This must be a response to both water pressure and current. The small value of such single observations is recognized but they are presented here because the opportunity to secure such data is small. In this river there are also notable relations between especially dry seasons and the distribution of other animals. The season in which the riffles were dry (October 31,1907) the pools presented. The Transverse Distribution of Stream Animals Fig. 64.—Shows the form of bottom and size of bottom materials in a cross- section of the North Branch of the Chicago River, a-d, natural size (original). a, a burrowing May-fly nymph (Hexagenia sp.). b, small bivalve (Sphaerium stamineum), two individuals, two views. c, viviparous snail (Campeloma integrum), seen from two sides. d, the long river snail, young and full grown (Pleurocera elevatum). Fig. 65.—Cross-section of the stream with reference to a curve. an unusual aspect. The standing pools were choked with water-net. The minuter forms, such as protozoa and flatworms, were present in the greatest profusion. Hydra was abundant. All this is in marked con- trast to the conditions which one finds when the stream is running. The season following the dry riffles, we found small Hydropsyche larvae, and a few young stone-fly nymphs. The only forms present were those that could be introduced by terrestrial, egg-laying Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Shelford, Victor E. (Victor Ernest), b. 1877; Geographic Society of Chicago. Chicago, Ill. : Publish
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
