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I have unfortunately had no opportunity of contributing to any great extent to this
work of clearing the path of study. The conditions brought about by the war were a decisive
obstacle to this. I have only succeeded in getting type specimens of a few previously described
species; see the préfacé.
The main object of this work of mine became consequently to make as large a nuinber
of species well known as possible. . . Altliough now that the first part of this work is nearing
its close I feel that I have not attained the precision and comprehensiveness at which I ventured
at one time to ahn, yet I put forward the results that I have obtained in the hope that the
descriptions given below may prove to be satisfactory both for certainty in the identification
of species and for establishing the positions of the forms in question in the natural system.
L. Plate, in his above quoted essay „Prinzipien der Systematik, etc.,“
1914, writes, p. 148: „Ganz allgemein läßt sich behaupten, daß die äußerlich sichtbaren Organe
der Tiere schon aus dem Grunde zur Diagnose besonders geeignet sind, weil sie viel
veränderlicher sind als die inneren. Nah verwandte Arten sind häufig nur an solchen Differenzen der
Hautskulptur, der Färbung, der Hautanhänge, der Schalen, der Sinnesorgane zu unterscheiden,
während sie in den inneren Organen gleich oder fast gleich gebaut sind. . . . Selbst Arten aus
verschiedenen Gattungen sind gar nicht selten an inneren Organen nicht zu erkennen.“
I have made the same observation with regard to the marine Ostracods. The external
characters are much more variable than the internai ones, a state of affairs that, as L. PLATE
writes (loc. cit.), is presumably due to the faet that the former „von dem beständigen Wechsel
der äußeren Faktoren in erster Linie getroffen werden“. As a rule only the higher systema tic
units differ from each other in the internal characters, such as the digestive organs, the inner
sexual organs, etc. One conséquence of this is that in the descriptions of species and genera
I have given below I have dealt almost exelusively with outer characters taken from the shell.
limbs, furca, the outer sexual organs and sensory organs. — The inner characters, the nervous
and the digestive systems, the inner sexual organs and musculature, which have been partly
worked out in a very meritorious way by preceding authors, for instance G. W. MULLER, 1894,
I hope to have an opportunity to deal with in more detail in a subséquent work in connection
with a comparative morphological study of these forms.
A conséquence of the incompleteness and uncertainty of the great majority of the
preceding descriptions of species is of course that it is at present often quite impossible to decide
the value of a character from a systematic point of view, i. e. it is impossible at present to
establish detailed family and genus diagnoses of a definitive nature. It is therefore necessary,
when more detailed diagnoses are now worked out, to burden the descriptions of species in many
cases with a multitude of characters of a higher systematic value, characters which may
gradually be transferred to genus or perhaps even to family diagnoses according as the nuinber
of the well described species inereases. In the cases where I had a comparatively abundant
material of the same family or genus at my disposai 1 worked out comparatively detailed family
and genus descriptions in order to avoid too much repetition. In these descriptions, which are
to be taken as quite provisional, I have collected all or at any rate most of the characters that
1 found common to all the species of the family or genus in question that were investigated
Difference between
external and
internal characters.
My descriptions uf
families and genera.
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