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Mandible.
parative embryology. It seems, however, to be by no means impossible, perhaps even rather
probable, that G. W. Müller was pretty near the truth when he assumed that the Pro
t-ostracods had a nine-jointed* exopodite, perhaps of about the same type as in the
recent P o 1 y c o p i d s. The reasons that seern to me to support this are, first, that the
forms which are now characterized by an antenna of this sort, Cypridinids,
Halo-c y p r i d s and Polycopids, are in several respects certainly to be considered as the
most primitive Ostracods, and, secondly, that the agreement in structure in these groups
is altogether too great to justify us in assuming a convergence, in the case of an organ of so
complicated a structure as this brandi. At any rate the ancestral forms of these three groups
probably had a similar exopodite on this limb.
The on ly statement about the second antenna of the
Prot-ostracods that we can make at present with almost complete
c e r t a i n t y, is, a c c o r d i n g to m y opinion, that i t p o s s e s s e d a w e
11-developed protopodite and a comparati vely strong exopodite
and endopodite.
We ought perhaps to note the great resemblances there is between this limb in the
Cyther ellids and the type that is presumably to be considered as the original one for
the two following limbs, the mandible and the maxilla. Perhaps this indicates that the
second antenna of this group represents a comparatively primitive type.
Was the endopodite in the males of the ancestral forms of Cypridinids,
Halo-cyprids and Polycopids developed as a seizing organ, as G. W. MÜLLER has assumed?
In the recent Cypridinids the whole of the end joint of the endopodite is pressed
against the preceding joint in seizing. In the Halocyprids, on the other hånd, the end
joint has a process in the shape of a seizing arm, which issues proximally on the joint. The
males of the Polycopids do not have the endopodite developed as a seizing organ ;
whether the wart-like process near the point of the endopodite which is found in this group
(cf. G. W. Müller, 1894, pl. 7, iig. 10) is homologous with the seizing arm in the
Halocyprids, as G. W. MÜLLER has assumed, I must leave undecided; there is no certain proof
of this homologization, G. W. MÜLLER does not give any and I have not found any myself.
In the face of these facts — that the Polycopids, in several respects presumably
the most primitive of these three groups, do not have this branch developed as a seizing
organ and that the seizing function has been carried into effect in different ways in the
Cypridinids and the Halocyprids — one must say that this assumption of
G. W. MüLLER’s is to be considered as rather uncertain.
Mandible: — G. W. MüLLER’s assumption that this limb in the Protostracods
was composed of two protopodite joints and three endopodite joints seems fairly probably;
* G. W. Muller points out. 189Î, p. 86 that „manche Arten weisen darauf hin, daß die Zahl ursprünglich
größer war (Philomedes)“. A careful study of soiue forms of this genus has eonvinced me that the chitinous structures
on the end-joint ol this branch (of the males), to which this writer refers, cannot probably be explained as traces of
a tenth joint. In addition it is to be noted that, cven il the genus Philomedes originally had a ten-jointed exopodite
on this limb, it is obvions that we have no right, because of this, io conclude that the Protostracods
originally had ten joints,
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