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fr’ijth lim b.
Sixlli Unib.
S evert ih Unib.
i ibralonj plaies.
Fifth 1 i ni b: — This appendage would have been of about the same type as that
of Macrocypris, a recent genus belonging to Cypridae, but it was probably furnished, however,
with a vibratory plate of about the same type as that which characterizes this limb in the
H a 1 o c y p r i d s. Its protopodite would have been fairly large and to a rather great extent united
to the body. Distally-anteriorly the protopodite would have been furnished with a short
process (explained by G. W. MULLER as the exopodite). Its exopodite*, which pointed backwards
and was fairly long, was four-jointed, with a small end-joint armed with three bristles. This
limb would have been used partly in taking up food and partly as a locomotory organ
„(An-klammern?)“. During its further development sometimes one and sometime the other of these
two functions was prominent. When the former function predominated the forward pointing
process on the protopodite was almost always completely reduced. When the taking up of
food became the principal function of this limb it was necessary, owing to the réduction of the
forward pointing process, for the limb to move forward to the boundary between the head and
the trank of the body (Cypridae) or even right up to the hypostome (Cypridinidae and I I alo
-cypridae), so that owing to its position it came to look like a limb of the head. In the males
of the ancestors of the families that are placed by G. W. MÜLLER in one group under the naine
of Podocopa the exopodite of this limb would have been already developed as an auxiliary
organ in copulation.
The s i X t h limb would in the Protostracods have borne the closest
resemblance to this appendage in the females of the Halocyprids. This limb of the
C y p r i d s, Darwinulids, N e s i d e i d s and Cytherids has been adapted to
a crawling life and especially on account of this has been lengthened. With regard to this limb
in the Cypridinids G. W. MÜLLER says tliat it is „nichts weniger als eine ursprüngliche
Form“. „Bei den P o 1 y c o p i d e n ging in Folge der starken Réduction der Körpergröße
dieses, sowie das folgende Beinpaar verloren.“
Seventh limb: — This appendage, which has two principal functions in recent
forms, namely those of a cleaning or a crawling organ, was already a cleaning organ in the primitive
forms and had about the same type as in the recent C y p r i d s. We find it developed as the
most complete cleaning organ in the Cypridinids; its chief task is to keep the
brood-chamber clean. In the Halocyprids it was originally a more perfect cleaning organ
than in the recent C y p r i d s; it was then reduced, „in Folge des Aufgebens der Brutpflege?“,
ln the N e s i d e i d s and Cytherids it became exclusively an organ of locomotion.
Yibratory plates: — These are arranged as follows in the recent Ostracods:
In Cypridinidae and Polycopidae on the fifth limb, in Halocypridae on the fifth and sixth limbs,
in other Ostracods they are situated farther forward, on the mandible and the maxilla,
less frequently on the fifth limb as well, in exceptional cases (Cytherella) on the sixth limb.
G. W. Müller assumes that the Protostracods had vibratory plates on the fifth and
sixth limbs of about the same type as in the recent Halocyprids or perhaps on the fifth,
sixth and seventh limbs. When these organs were reduced on the posterior limbs similar ones
would have appeared „compensatorisch an Mandibel und Maxille“. As evidence for this opinion
* Endopodite according to tliis nulhor’s interpretation.
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