Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXIII (1927)
Harring, H. K.; Myers, F. J.
The rotifer fauna of Wisconsin. IV. The Dicranophorinae, pp. -Plate 49 ff. PDF (41.5 MB)
672 Wisconsin Academy of Sciences, Arts, and Letters. Ho surface of the globe. Our primary concern is then with the conditions of existence. Their importance became con very evident when, some 15 years ago, we began to compare aWrE the lists of the rotifers found around Washington and in stai the neighborhood of Atlantic City. The differences were the so great that we were completely at a loss as to how to ac- rd count for them; hardly any species were to be found onf are both lists. The conclusion that there must be important atio differences in the environment seemed unavoidable; no zoic geographic or physiographic barriers intervene to prevent und a thorough mixing of the two faunas; the differences were ean tentatively attributed to the water and the substances pres- nun ent in solution, derived from the soil, but there was very little in the way of actual facts to start with. We knew that the natural waters of the region around Washington are moderately hard and of the New Jersey Coastal Plain at Atlantic City very soft. The District of Columbia, ac- tually almost synonymous with the city of Washington, is on the dividing line between the Piedmont Plateau and the tertiary lowland; the soils are miinlyT unconsolidated cre- taceous clays, sand and gravel, eroded and transported from the plateau. The surface waters are generally classed as moderately hard, containing appreciable amounts of calcium and magnesium salts in solution. The New Jersey Coastal Plain is a post-glacial elevation of the slightly sloping ocean bottom and the soil is sand; the sur- fne waters arep all acid and their solid contents extremely suit had was wit] diox A Covi This gen port plan fers, prov cent ifi-1 low. ent The difference between "hard" and "soft" water is line; mainly the relative amount of dissolved calcium carbonate, mop( so the most obvious line of attack Dwas a determination of speci hardness and also of the total available carbon dioxide. drop This was continued for some time, until it seemed doubtful smal that any explanation would be forthcoming. The differ- cies. ence between hard- and soft-water rotifers could always noun be found; a glance at a collection told its origin at once. main Rbil- the transition from one to the other was entirely too wnt. sharp, and, in addition, there were differences between hard-water rotifers and between soft-water rotifers that could not be explained by and did not agree with the varia- tions in the amount of dissolved calcium salts. tions forni Lake nette I. Ahk
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