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Statements
oj frequency.
Plankton samples.
Statements oj
locality.
H istorical resumés.
Final remark.
joints, the figures above the line dénoté the relative length of the joints on the dorsal or anterior
side, the figures below the line the relative length of the joints on the ventral or posterior side.
I may point out in passing that when I speak below of bristles that are more or less
finely pectinated distally, this pectination is presuuiablv always in two rows, even if it is
shown in one row in the dra wing; the two rows of spines are of ten situated on the same side,
so that what is apparently one row of pectination seems to be present. This pectination could,
of course, only be reproduced in outline.
It is often rather difficult to estimate the number of bristles because they are situated
so close together. G. W. MÜLLER complains about this, 1894, p. 28 . . . . „Wer die
Schwierigkeit einer genauen Feststellung dieser Verhältnisse kennt . . . .“ I think I have overcome
this difficulty, at least partly, by a simple manipulation: the limb (in glycérine) is crushed
by a slight pressure on the cover-glass and then the latter is moved, if desired, in different
directions. By this procedure bristles that are placed close to each otlier are separated. I have
obtained very good results with this method. Chitinous parts ought not to be reproduced from
i’resh material; the material ought first to be hardened in alcohol, or else the chitinous parts
are too strongly compressed by the cover-glass and misleading images arise.
In the descriptions given in this work the penis is described rather superficially,
but I hope that the drawings that are given of this organ will, in spite of their being done in
outline, prove to be sufficiently detailed to permit of quite certain identification of species.
I hope to have an opportunity in a subséquent work to give more detailed descriptions and
reproductions of this organ which is so interesting from a morphological point of view.
Although it is almost always statecl below how many specimens of each species were
caught, this information cannot be used, except with very great caution, as an indication of
the frequency of the forms in question, as the samples that were investigated were not collected
for comparative quantitive investigations.
All the plankton samples were caught in open nets. The statements as to depth given
under these forms are consequently of comparatively little value.
Ail statements as to the longitude of the localities are made with reference to Greenwich.
A historical resumé is given after each of the higher systematic units, sub-families,
families, etc. These resumés deal chiefly with the historical development of our knowledge
of the classification of the Ostracod group and the organs that are most important for the
special classification, the shell, appendages, external sensory organs, etc.
Before ending this introduction and giving the results of my investigations I wish to
quote a statement made by Til. MORTENSEN in his distinguished work on the Echinoids of the
Ingolf Expedition, 1903, p. 3: ,,]) et viste sig, at Dyrene var saerdeles gode
at have med at g <> r e, A r terne meget vel karakteriserede. Det e r
Literaturen, der bringer Vanskelighederne gennem den Uend
e-lighed af daarlige Beskrivelser, den ru m in e r.“* This remark coïncides
entirely with the expérience I obtained myself in carrying out the present work.
* Translation: The animais proved to be very good
I he li lera ture that < anses difficulty on accounl of the great
lo work with. the species yvere very well distinguished.
number of poor descriptions it contains.
lt is
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