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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 671


letters.
Notommat-
)rotrusible;
le to thrust
th or more.
3Menus Itura
ier isloated
n this sub-
quent mod-
hyrias and
Lent, rather
ind in this
the ventral
~ces for the
rngeal rods
;en that the
persistent
indurated
Beauchamp
ica and the
the differ-
iing; there
lopment of
specific im-
discovered.     |
ura and in
responding
)rds of the    I
glandulate     |
he circum-
recourse:
IS not been
I by other
that they
ific charac-
one of the
)up of ani-
dion. This
I
  Harring & Myo;.'-Rotifer Fauna of Wisconsin.-IV. 671
was ruled out in the very beginning by Ehrenberg, as far
as the rotifers are concerned; his travels in Egypt and
Nubia with Hemprich and later in Siberia with Humboldt,
combined with the study of the fauna in the neighborhood
of Berlin, proved to him that the same "Infusionsthier-
chen", which included protozoa, diatoms, desmids and roti-
fers, were to be found anywhere on the face of the earth
if water was present and a diligent search made for them.
This view was propounded in spite of the already then well
known fact that the higher groups of the animal kingdom
exhibit very evident discontinuities and localizations in their
distribution on land and in the ocean, caused by barriers
of various kinds, dependent on the means of dispersion
available to the group in question. However, the lower we
descend in the scale of organization, the more effective and
the more varied become the means of distribution, the bar-
riers losing correspondingly in importance. The prevalent
impression that the microscopic animals are cosmopolitan
and that their distribution is not a problem, is therefore
not difficult to account for, especially if the unsatisfactory
condition of "invertebrate" taxonomy is considered;' zoo-
geographic speculations are bootless without adequate de-
scriptions of the species concerned.
  As the rotifers are so readily transported, they have al-
ways been pressed into service as typical examples of a
cosmopolitan group, whenever such wvere needed. This
continued until Jennings published his Rotatoria of the,
Great Lakes, in 1900; although formally accepting the uni-
versal distribution theory, he emphasized the importance
of variations in the environment. "The problem of the
distribution of the Rotifera is, then, a problem of the con-
ditions of existence, not a problem of the means of distri-
bution". We believe, on the strength of our own observa-
tions, that this is a correct statement of the problem. "Po-
tentially cosmopolitan" the rotifers probably are, but, as
used by Jennings, this refers principally to the means of
distribution.
  The rotif ers must of necessity be a very old group, and
we are evidently justified in the inference that any given
species has at some time in the past had abundant oppor-
tunities to reach any given spot on the present-day land
i nrated            ip fers, iere to bte microscopic animal face of the earth
Beahasmu-            if water was present and a diligent search made for
them.
                     oThis viewl was propounded in spite of the already then
well
hyrias and           known fact that the higher groups of the animal kingdom
Lent, rather         exhibit very evident discontinuities and wocalizations
in their
                   Idistribution on land and in the ocean, caused by barriers
ind n this           of various kinds, dependent on the means of dispersion
the ventral          availabl the rotie group in question. However, the lower
we
ces for the          descend in the scale of organization, the more effective
and
     ngeal rods    othe more varied become the means of distribution, the
bar-
;en that the         riers losing correspondingly in importance. The prevalent
persistent          impression that the microscopic animals are cosmopolitan
indurated           and that their distribution is not a problem, is therefore
the dircer-
Bracoamrne:          diffionstofoexistenceonoteapproblem of the mensaoftisfatori-
notbeene           bundtion"  We beieveonthe streonghofy our cowns observa;o-
thegdifhere         geographic speculations are bootless without adequate
de-
inythere    *        scriptions of the species concerned.
that they tentiaycosmoptAs the rotifers are so readily transported, they
have al-
     ;pecifie im-ways been pressed into service as typical examples of a
                     pefi mcosmopolitan group, whenever such wvere needed.
This
discovered.          continued until Jennings published his Rotatoria of
the
ura and in           Great Lakes, in 1900; although formally accepting the
uni-
responding          versal distribution theory, he emphasized the importance
)rds of |hT of variations in the environment. "The problem of the
glandulate           distribution of the Rotifera is, then, a  problem of
the con-
he circum-            itions of existence, not a problem of the means of
distri-
         *ecoursSe bution". We believe, on the strength of our own observa-
IS not been          tions, that this is a correct statement of the problem.
"Po-
I by other           tentially cosmopolitan" the rotifers probably are,
but, as
that theY          cused by Jennings, this refers principally to the means
of
                       The rotifers must of necessity be a very old group,
and
one of the           we are evidently justified in the inference that any
given
)up of ani-          species has at some time in the past had abundant oppor-
)Pon. This          tunities to reach any given spot on the present-day land
           in  Thi


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