Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
should not be given too much importance. With regard to the value of the former character
the following facts may be instructive. In Thaumatocypris the first antenna is situated
somewhat deeper down than in other Halocypriformes. In Cypriformes we find forms
with both high and low places of attachment; this antenna of the Cypri ds is fixed „hoch
oben an der Stirn“ (G. W. MÜLLER), while in the Cytherids and N e s i d e i d s it shows
a resemblance to that of the Cypridinids „besonders in der tiefen Einlenkung an der
Stirn“ (G. \\. MÜLLER, 1894, p. *29). With regard to the way in whicli the sexual organs
open, we may, in the first place, mention the important differences that are actually
to be observed between Polycopids and H a 1 o c y p r i d s, and, secondly, that
the Cytherellids are also characterized by an unsymmetrical exit of these organs
(Note too the resemblance — superficial, it is true — that exists between the copulation organ
in Cytherellids and Halocyprids). I do not think G. W. Müller would bring
forward this character as a sign of close relationship between Cytherellids and
Halocyprids. In my opinion it is not at all impossible that we have here a phenomenon of
convergence.
H alocypri formes, Cypridinif ormes and Polycopi formes are probably to be regarded
as three groups fairly independent of each other. That nevertheless they resemble each other
not inconsiderably in a number of characters is due, first, to the fact that in several respects
they show primitive featurs, and, secondly, to convergence.
It seems difficult to decide which of these three groups is to be taken as the most
primitive. The facts of the matter are probably that each group is in a number of respects
more primitive than the two others, while in other respects, on the contrary, it is more
developed. Thus, for instance, Cypridinif or mes are presumably primitive inasmueh as, let us
say, the lateral eyes, median eye, the heart and the two posterior limbs are developed, but they
differ from the original type in having a rostral incisur and a rod-shaped organ, and in the
structure of the second antenna and the maxilla. P oly copif ormes, which have no lateral eyes,
médian eye, heart or two posterior limbs are, on the other hand, presumably primitive with
regard to the rostral incisur, the rod-shaped organ and the structure of the second antenna
and maxilla.
It is at least equally difficult, perhaps even more so, to détermine with certainty the
natural position of the Cytherelliformes in the Ostracod system.
G. W. MÜLLER placed this group together with the families Cypridae, Darvrinulidae,
Nesideidae and Cytheridae. The same author points out in his work of 1894. p. 190. that the
Cytherellids show „wenige, aber immerhin beachtenswerthe Beziehungen zu den
Cypride n“. The characters by which this group would show agreement with Cypriformes
are the following: Second antenna: The group of sensory bristles on the first joint of the
endopodite and the group of five bristles distally on the inside of the same joint. The use of
the fifth limb as a clasping organ in the males.
Wh at value can we assign to these characters from a classificatory point of view?
Second antenna: With regard to the second antenna it ought to be pointed out
that similar sensory bristles are also found in the Cytherellids proximo-posteriorly on
Cytherelhjorntes.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
