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has four joints. According to this writer’s work of 1891 a, p. 21, on the other hånd, this antenna
has five joints; it consists of „einen zweigliedrigen, stielförmigen Schaft und eine dreigliedrige
Geißel“. — In G. W. MÜLLER’s work of 1890 a this antenna is stated (p. 258) to have five joints;
according to the same investigator’s work of 1894, p. 25, on the other hånd, it has only four
joints, but it was pointed out that sometimes „noch ein 3. kleines Glied am Ende des Stammes
mehr oder weniger deutlich abgegrenzt ist“; in his work of 1912 G. \V. MÜLLER gives four as
the number of joints in this antenna.
We find the same differences with regard to this antenna in the genus Halocypris.
All these authors have obviously fiuctuated between two alternatives: a four-jointed
or a five-jointed first antenna; by the two former authors the latter alternative was adopted; in
G. W. MÜLLER’s later works, on the other hand, the former alternative prevailed.
The question at issue is clearly whether the little collar-like part distallv of the second
joint ought to be counted as a special joint or if it ought to be taken as a part of the second joint.
Which explanation is correct? It seems to me that it is almost a matter of taste. In all the
species of the above-mentioned two genera that I investigated this part had no special
muscles at all, no muscles are limited to it and none are attached on its proximal boundary.
I have nevertheless taken it as a special joint in this work. This is due to the faet that in
a number of forms it is exceedingly well marked ofï; cf„ for instance, fig. 8 of Halocypris brevirostris.
I could not find any guidance towards the solution of this problem from the third genus of this
family Euconchoecia that I had an opportunity of investigating.
Is it possible to carry out a quite certain homologization of the joints of the first antenna
in the genera belonging to the Conchoecinae’i
In the case of the genera Halocypris and Conchoecia these joints may with great certainty
be homologized. — The highest number of joints on the first antenna in the latter genus
is five, and tliere does not seem to be the least doubt that these joints are homologous
to the five joints that characterize in most cases this antenna in Halocypris. This assumption
is supported both by the bristles and the musculature of this limb.
The number of bristles is, as we know, quite the same in these two genera: the first and
third joints have no bristles at all, the second joint has a single bristle dorsallv and the fourth*
and fifth bristles have two and three bristles respectively. In addition these bristles are of
about the same type in the genus Halocypris as in the females of Conchoecia.
All the species of Conchoecia investigated and described by me below have a practically
identical muscular system in this antenna. It is true that slight exceptions from the type
described below can be observecl, but these are of no importance for this question, so that they
are not mentioned here. In the males of this genus we find the following muscles in this antenna
(type: C. symmetrica G. W. MÜLLER; ef. fig. 7 of this species): The first joint contains two
muscles. One of these, the extensor of the second joint, is very strong, simple, and has the nature
of almost a pure extensor; proximally it is attached dorso-proximally on the first joint, distally
on the second joint dorso-proximally, somewhat laterally. The other of these two muscles is
also strong, in most cases divided into two (only exceptionally into more) well defined parts,
* With regard to a larger number of bristles in Conchoecia serrulata see the remark on tliis species below.
Zoolog, bidrug, Uppsala. Suppl.-Bd. I.
Homologization of
the joints of the first
antenna.
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