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this autkor points to the reduced vibratory plates on the posterior limbs in Ntsideidae and the
conditions in the Cytkerellids.
The brush-shaped organ is considered by this writer to be homologous with
an eighth limb. This limb would have been found in both males and females of the
Prot-ostracods and have belonged to the segment behind that of the seventh limb. The position
of this organ near or just behind the fifth limb is considered to be a secondary one.
The f u r c a of the Protostracods would have been of about the same type
as this organ in Conchoecia.
This author does not express any opinion about the sexual organs.
In this Connection he does not mention the rod-shaped organ eitlier. It is
merely stated on p. 161 that this organ is „lediglich“ homologous in Cypridinids and
Halocyprids.
Althougk this view of the life, organization and the development of the
Protostracods, as worked out by G. W. MÜLLER, is very meritorious, it is, nevertheless,
open to criticism in many details.
According to this author the Protostracods swam freely. H o w did
t h e y s w i m?
We can distinguish three types of swimming in the recent Ostracods; first the
method of swimming found among Cypridinids and most Halocyprids, secondly
the method of swimming in the Cy prids and P o 1 y c o p i d s, and thirdly that found in the
genus Tliaumatocypris. The Cy p ridinids and most of the Halocyprids use what one
might call rostral incisur swimming. They do not use the first antenna as a natatory organ,
a faet that was pointed out by G. W. MÜLLER in 1894, p. 23: „irgend welchen Antheil an der
Schwimmbewegung nimmt hier die 1. Antenne sicher nicht.“ I have also been convinced of
the correctness of this observation by examination of living animais. It is to be noticed, in
addition, that the structure of this antenna makes it anything but suitable for a natatory organ.
Thus G. W. MÜLLER writes, 1894, p. 24: „Auch ihr Bau macht mir eine Mitwirkung daran
wenig wahrscheinlich.“* On the other hand the second antenna, which is the onlv natatory
organ of these forms, is particularly well suited by its organization to fulfil this function. It
is very powerful, its protopodite is very large and full of powerful muscles which move the
exopodite. This is long and cylindrical and is fitted with long, powerful natatory bristles and
joined very loosely to the protopodite. Each valve in these forms is fumished anteriorly with
an incisur, the rostral incisur, and in swimming the exopodite rests with its basal joint in this
almost as an oar rests in a rowlock.** In swimming the exopodite moves almost straight out
at the sides and backwards, only slightly downwards; in this way a straight forward motion
of the animal is produced. The endopodite of this limb is more or less reduced in these forms
and does not play any part in swimming. In the C y p r i d s that have no rostral incisur both
the first and the second antenna take part in swimming. The first antenna is long, cylindrical
* G. S. Brady and A. M. Norman assume, however, 1896, p. 625, that this linib is nsed in swimming.
** Of course I do not mean by this that the action in this kind of swimming is the same as in rowing. On lin
contrary this is not at all the case.
Rrusli-shaped organ.
Furca.
Sexual organs.
Rod-shapcd organ.
A criticism uf G. 11 ’.
Müller’s vtetv of ih c
Protostracods.
Il otv did the
Protostracods movcl
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