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G. II. Müller’s
opinion of the P
rot-ost racod s.
Life.
Shell.
Segmentation of the
body.
/feart. Alimentär y
organs. Eyes.
\ umher of limits.
First antenna.
Second antenna.
these, C. CLAUS and G. Alm. For this reason it seemed to me that the most obvions course in
discussing this problem was to put my answer into the form of a criticism of G. \Y. MüLLER’s
exposition of the results gained by him.
G. W. MÜLLER depicts the life, Organization and development of the Protostracods
on the whole as follows:
The Protostracods were freely swimming organisms, but did not travel far
from the bottom, often attaching themselves to hydrophytes „ohne indessen umherzukriechen“*.
They already had a calcified sh eil which enclosed the whole body and which was shut
by a closing muscle which went through the body. The shell was „vermuthlich“ characterized
by a rostral incisur „für den Austritt des Außenastes der 2. Antenne“ and by an arched ventral
margin.
The body was segmented externall y; there were at least eleven segments
behind the head, of which only some had limbs.
A heart was developed. The alimentary organs were of the same simple
type as in the recent Cypridinids. There were well-developed compound lateral
eyes and an unpaired median eye divided into three parts.
There were eight pairs of limbs, and a ninth had perhaps already beeome employed as
a copulatory organ. Only four of the limbs belonged to the head; the appendage corresponding
to the second maxilla of other Crustacea was absent.
The first antenna had eight joints. It was probably most similar to that of the recent
Cypridinids, which is a sensory and a locomotory organ at the same time. „Von einer
solchen Form konnte sich ebensowohl die vorwiegend der Bewegung dienende Form der
Podo-copa, wie die ausschließlich oder fast ausschließlich als Sinnesorgan fungirende mancher
Myodo-copa entwickeln. Unzweifelhaft hat ein Wechsel, der zum Ueberwiegen der einen oder anderen
Function geführt hat, wiederholt stattgefunden.“
Second antenna: —- This had a two-jointed protopodite and a
well-developed endo- and exopodite. The endopodite was four-jointed, the exopodite composed of a
rather large number of joints. Of the recent Ost r aco d s the Polycopids would
have the most primitive second antenna; these forms would differ from the original type chiefly
in the structure of the protopodite. The protopodite of this limb would have had a very different
fate in the C y p r i d i n i d s, Halocy p r i d s and Polycopids on the one hand
and in the other Ostracods on the other. In the former groups the two protopodite joints
have pointed in the same direction and then gradually have been quite united to each other.
In the latter the protopodite was distinguished by the fact that the two joints together formed
an upward pointing knee; in most of tliem it became single-jointed afterwards by the total
disappearance of the distal joint; this joint is still fourni only in the genus Cytherella. In the
( ’ y p r i d i n i d s and the Halocyprids the endopodite is more or less completelv
reduced. „Daß bei einer fast ausschließlichen Verwerthung der 2. Antenne als Schwimmfuß
* G. W. Müller writes, p. 198. that they were „in der Lebensweise den H alocypriden am nächsten".
VVlien he wrote this, lie was of the opinion that the Halocyprids live chiefly al the bottom and „nur
zeitweilig schwimmend aufsteigen“, 1894, p. 19; of course he gave up this opinion later on.
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