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seems to be quite unsupported. With regard to this it ought to be enough to point out that
this limb is not developed as a seizing organ in two of these families, namely Nesideidae and
Cytheridae, and that the sixth limb in the males of Cytherdla even shows a closer resemblance
to the fifth limb of the C y p r i d s than does their fifth limb.
It is possible that the position of the fifth limb of Cypridinids and H a 1 o
cypri d s, where it is placed far forward, is, contrary to G. W. MÜLLER’s view, to be considered
as original. This assumption of G. W. MÜLLER’s is, of course, connected with his supposition
that the limb corresponding to te second maxilla of other Crustacean groups has disappeared
in the Ostraeods.
Sixth limb: — There is the saine uncertainty with regard to this limb as with the
preceding one. The assumptions that the foliaceous type of the Cypridinids is original
and that the rod-shaped type is the most primitive are opposed to each other in this case as
well. The fact that with regard to this limb too there is a very great agreement between
the Halocyprids on the one hand and Cyprids, Darwinulids, N e s i d e i d s
and Cytherids on the other makes the assumption that the resemblance between these
limbs is due to convergence seem very improbable.
It seems to be impossible to make any detailed statement at present as to the cause
of the disappearance of this and the following limb in Polycofidae. G. W. MÜLLER assumes
that it was due to the smallness of these forms. It is to be noted that these limbs are also
reduced in the C y t h e r e 11 i d s, although these are comparatively large forms.
Seventh limb: — Contrary to the two preceding limbs the seventh one never has a
foliaceous type in the recent Ostraeods. In Cyprids, Darwinulids,
Neside i d s and Cytherids it is of about the same type as the fifth and sixth limbs; in the
Halocyprids itis certainly short, but all the same it is rod-shaped; in the
Cypridinids, the group in which the fifth and sixth limbs are of the foliaceous type, it is developed
as a long, vermiform amiulated appendage. (In the Polycopids and Cytherellids
this appendage is, as we know, not found at ail.) These facts seems to support G. W. MÜLLER’s
assumption that this limb was originally of the rod-shaped type; it was perhaps, as this
investigator assumed, of about the same type as in the recent Cyprids. This fact may
also perhaps be considered to support the assumption that the rod-shaped type was also
original for the two preceding limbs.
Was this limb developed as a crawling limb in the Protostracods or did it act
as a cleaning organ? G. W. MÜLLER assumes, as we have seen above, that it was used as a
cleaning organ; other investigators, e. g. G. Alm, 1015, assume that it only adopted this function
later. Which of these views is to be considered as correct?
G. Alm puts forward the following reasons for his view (pp. IS— 21): In the N e s
i-d e i d s and Cytherids this appendage is used as a crawling limb, not as a cleaning organ.
In the Darwinulids it is possibly used as a cleaning organ, but probably, at any rate,
this function is only to be considered as secondary, crawling being the most important function.
In the Cyprids we find in the lower forms that this appendage, although developed as a
cleaning organ, „nach ihrer Lage zu urteilen sowohl als Bein wie als Putzfuß anwendbar ist“
Sixth limb.
Seventh limb.
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