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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. [667]-Plate 49 ff. PDF (41.5 MB)

Page 672

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
low.                                                                 ent
  The difference between "hard" and "soft"
water is 
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.
I. Ahk

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