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.
claws. Finally the Cytherellids have, it is true, rather short and broad and powerful
furcal lamellae, armed with rather numerous claws, but the furca in tliese forms is of quite a
different type from that found in Cypridi nids and Halocyprids.
Which of these types is to be considered the most primitive?
I consider it rather improbable that the very small furca in the Cytherids
represents a primitive condition. Presumably a réduction has taken place in these forms (possiblv
in connection with the powerful development of the posterior limbs). The different development
and type of the furcal lamellae and the great variation in the number and development of the
furcal claws in the other groups seem to indicate that, in spite of the faet that it
presumably had comparatively well developed lamellae, the furca of the Protost r a cods was,
all the same, very slightly differentiated ; presumably it wTas armed with only a few claws.
The following facts also seem to support this assumption. Thaumatocypris, which is, in many
respects presumably the most primitive genus among all Halocyprids, has a furca that
consists of two relatively short, broad and powerful lamellae — like that of other
Halocyprids. Each of these lamellae is armed with only two claws, situated distallv; behind
these claws there is only a number of short spines. What perhaps strikes the observer of this
furca more than anything is its great resemblance to the furca in a closely-related group of
animais — the Cladocera. Without going so far as to say that this furcal type is the
most primitive, I wish, however, to point out one faet that may perhaps be considered
to point in this direction. In investigating the post-embryonal development of the C y p
ridi n i d s I observed that both in the sub-genera Doloria and Vargula and in Philomedes the
youngest freely living larval stage is characterized by a furca consisting of two relativelv short
and broad, but powerful, lamellae; each of these lamellae is armed distallv with two rather
long and powerful claws, behind which there follow a number of short and weak spine-like
claws; cf. the special part of this work, fig. 21 of Philomedes globosa and fig. 14 niCypridina
(Doloria) pectinata; only during the larval stages that immediately follow do these claws grow,
so that in these stages the transition between the distal and the proximal claws becomes
uniform. G. \Y. Müller made the same observation (1894. p. 185) in the representatives of the
Cypridinid group investigated by him, species of Vargula, Philomedes, Pseudophilomedes,
Sar-siella and Asterope; ci’., for instance, G. W. MUller’s figure of a larval furca of the genus
Aster ope, 1894, pi. 34. fig. 53. C. CLAUS, 1893, showed that the same condition is also
charac-teristic of the Halocyprids (p. 286). „Das jüngste der beobachteten Stadien, leider nur
ein einzigesmal aufgefunden .... besitzt nur 2 Paare von Furcalklauen.“ During the first
freely living larval stage these forms thus have a furca whose type differs very much from that
of the mature individuals, but which shows, on the other hand, a comparatively close
agree-ment with the furca in Thaumatocypris. — It is to be noted that the genus Thaumatocypris
was unknown to G. W. MÜLLER in 1894.
As will be seen from what has preceded, G. W. Müller does not say anything about
the sexual organs of the Protostracods. This problem has rather great
difficulties. On accoimt of the conditions in the recent Ostra c ods and closely related
Crustacean groups, it seems to me most probable that both the testicles and the ovaries in
Some additional
remarks about tb
nrganizatinn of tli
Protostracods.
Sexual organs.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
