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It is true that the furca in Myodocopa is of a relatively uniform type, but, as is shown
on p. 95 above, it is by no means impossible that we are dealing here with a phenomenon of
convergence. In Podocopa this organ is subject to very considérable variations.
The sexual organs vary very considerably in botli Myodocopa and Podocopa
and it is certain that they cannot be adduced as evidence either for or against the
classification made by G. W. MÜLLER. These organs seem to be rather primitive in Myodocopa.
Nor can the alimentary organs be used in support of G. W. MÜLLEr’s view. The type
found in Myodocopa seems in all probability to be comparatively primitive. These organs are
not known in the Cytherella.
A heart is found in Cypri di nids and Halocyprids, but is absent in
Polycopids and Podocopa. It existed in the Protostracods.
Lateral eyes are only found in Cypridinids. They were certainly to be
found in the Protostracods. A median eye is found in Cypridinids and
most Podocopa. It existed in the Protostracods.
The rod-shaped organ is found in Cypridinids and Halo-
cyprids, but is absent in the others. In the two former groups we are presumablv
con-cerned with a phenomenon of convergence; see p. 96 above.
Are there any other organs that might be used to support this classification of G. \Y.
MÜLLER’s? This question must, I think, be answered in the negative.
It will be seen from this that G. W. MÜLLEr’s statement that the recent O s t r
a-c o d s can be divided into two sharply differentiated natural main groups can scarcely
be considered as justified. The characters on which he based his assumption are partly
such as he himself considered primitive and partly such as we have reason to believe have
arisen by convergence.
In my opinion the Cypridinids, Halocyprids, Polycopids
and Cytherellids form four well differentiated groups. The
C y p r i d s, Darwinulids, Nesideids and Cytherids are, o n the other
hånd, comparatively closely related to each other; they might
c o n v e n i e n 11 y b e i n c 1 u d e d in a higher classificatory unit, b y
the side of the four groups mentioned above. Thus, in my opinion, the
Ostracods ought to be divided into five main groups*.
This view coincides on the whole with that of G. O. Sars; it really differs from this
author’s view only by the division of the Myodocopa into two groups, équivalent to the three
other groups, the Cypridinids and H alocyprids having been separated. It agrees
with C. CLAUS’s view inasmuch as the Halocyprids are not grouped with the C y p r
i-d i n i d s in a higher classificatory unit but differs from it because these two groups are taken
as sub-orders and because each of them is considered to be parallel to the group composed of
the united families Cypridae, Darwinulidae, Nesideidae and Cytheridae.
The question as to whether these five groups are to be considered as being of quite the
same classificatory value cannot be answered at present with eertainty.
* With regard tu t he charaeterization ui’ these groups 1 need onl> refer liere lo the g ro up diagnoses given helow.
Furca.
Sexual organs.
Alinienlary organs.
/1 rart.
F!,es.
/(od-shaped orga n.
(Jther organs.
Summary of my
rrtl-icis/n of G. W.
Müller’s opinion thai
the recent Ostracods
are to he di c ided mto
Hvo main groups.
The main groups oj
the recent Ostracods
according to in y
opinion.
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