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Sevenlh Unib.
Cypridae,
Darwinulidae,
Nesideidae and
Cytheridae.
Halocypridae.
Cypridinidae.
of bristles that is fourni in most cases on the posterior edge of the protopodite and that was
taken by me above to be a remains of a vibratory plate appears, according to a statement on the
same page, to belong to a reduced vibratory plate. This assumption has later been adopted
by G. W. MÜLLER. Neither of these two authors has tried, however, to give any proof for
their views. — With regard to the morphological value of the vibratory plate — just as in the
case of the same organ on the fifth limb — we find two different views in the literature; most
writers — if they have any opinion in this matter — take it to be an exopodite; G. W. MOLLER
assumes that it is homologous to an epipodial appendage. The backward pointing part of this
limb, the part which is rod-shaped in H a 1 o c y p r i d s, C y p r i d s, Darwinulids,
N e s i d e i d s and C y t h e r i d s, is taken by all writers to be an endopodite. With regard
to this limb in the family Cypridinidae G. W. MULLER assumes, 1894, p. 68, that the proximal
joint, with two endites, corresponds to the protopodite, the three distal joints to the endopodite.
Curiously enough G. W. MÜLLER seems to have been very sure about the extension of the
protopodite. Thus he writes on this point, loc. cit. „so ist es wohl unzweifelhaft, daß bei
Cypridina das 1. Glied, welches an seinem Vorderrand 2 Höcker mit Borsten hat, als
Stamm ... zu bezeichnen ist“. The reason why G. W. MULLER and I have arrived at
somewhat different ideas as to the morphological value of this limb in the family Cypridinidae
is probably to be fourni in our different explanations of the fifth limb in this family. Just as
I have done above, G. W. MÜLLER has completely applied the homologization of the fifth limb
to the sixth one. Other investigators too have assumed that the distal part of the sixth limb
in the Cypri dinids corresponds to the endopodite, but they have not indicated the
exact boundary between the protopodite and the endopodite.
Seventh limb: — This is not found in the Polycopidae and Cytherellidae.
The families Cypridae, Darwinulidae, Nesideidae and Cytheridae: In these families the
seventh limb shows such a far-reaching agreement with the two preceding limbs that it seems
to me that there are no serious objections to applying quite the same homologization to this
limb as well. According to the first method of explanation the backward pointing
rod-shaped branch is to be considered as an exopodite, according to the other it is to be taken
as an endopodite and the part situated proximally of this branch is homologous to the
protopodite. No organ is ever developed that could be considered as an endopodite
according to the first method of explanation. The vibratory plate, which according to the first
explanation is to be homologized with an epipodial appendage, according to the second with
the exopodite, is always reduced; it can, however, be traced in most cases as single bristles
on the posterior side of the protopodite, situated sometimes proximally, sometimes distally.
No endites are developed.
It seems impossible to decide with certainty at present whether the very much reduced
seventh limb in the Halocyprids is to be taken as a protopodite + an exopodite or only
as an exopodite, according to the first method of explanation, or as a protopodite -f- an
endopodite or only as an endopodite, according to the second.
It is rather probable that the peculiar worm-like cleaning organ in the family
Cypridinidae is also to be taken as a rod-shaped limb consisting of a protopodite and
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