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the comb as a whole or at least the greater part of it is homologous to the joint that is denoted
by me above as the fourth exopodite joint; the long bristle (or the two long bristles) on the
lateral side of the comb is, according to the same statement, part of the outer lobe of the joint
that is termed by me the third exopodite joint.
After having had an opportunity of studying the fifth limb of the genus
Pseudophilo-medes G. W. MÜLLER, however, altered his opinion. Thus he writes, 1894, p. 63: „Ueber die
Morphologie des Fortsatzes habe ich an anderem Ort die Ansicht geäußert, daß er vielleicht
homolog dem Glied 4 sei, wobei ich mich auf die Aehnlichkeit mit der 2. Maxille der von
Philomedes stützte; hier sehen wir das 4. Glied nach vorn gerichtet. Die einzelne Borste, welche
auf dem äußeren Rand des Blattes entspringt,............sollte den hinteren Borsten von Glied
3 entsprechen. Zu einem anderen Vergleich giebt Pseudophilomedes die Veranlassung. Der
Fortsatz entspricht in Richtung und Lage dem stark verlängerten Zahnfortsatz von
Pseudophilomedes; der Haken an der Basis würde dann dem inneren (vorderen) Zahn, die Borste dem
Glied 4 entsprechen. Die Aehnlichkeit in der wechselseitigen Lage der einzelnen Th eile ist
auffällig genug. Giebt man die Möglichkeit zu, daß sich ein Zahn in einen borstentragenden Fortsatz
umwandelt, so erscheint dieser Vergleich zutre fiender als der ältere. Einstweilen muß wohl
die Frage in Ermangelung entscheidender Zwischenformen als offen betrachtet werden“
(cf. G. W. MÜLLER, 1894, p. 60, fig. 6). In the statement just quoted joint no. 4 corresponds
to joint no. 7 in the statement of 1890; joint no. 8 in the statement of 1890 corresponds to the
outer lobe on joint no. 3 in the statement of 1894. The „Zahnfortsatz“ corresponds to the
second joint on the part of this limb in the Cypridinidae that was termed the exopodite in the
homologization that I carried out above for this farnily. Joint no. 4 in the statement just quoted
corresponds to the joint that, according to the terminolog}" used by me above, is denoted as
the fourth joint of the exopodite. According to G. W. MÜLLER’s last statement the comb
is thus to be considered as homologous to the second joint of the part that is termed by
me above as the exopodite, the long bristle (or the two long bristles) on the outer side of
the comb is, according to the same statement, part of the joint termed by me the fourth
exopodite joint.
The faet that G. W. MULLER writes: „Giebt man die Möglichkeit zu, daß sich ein Zahn
in einen borstentragenden Fortsatz umwandelt“ seems to indicate that this author has started
from the assumption that the primitive forms of the family Asteropidae were characterized by a
fifth limb of about the same type as in the genus Pseudophilomedes. This can, however, scarcely
have been the case. Although, as has been shown in another part of this treatise, of all the
recent forms so far known the sub-family Philomedinae is probably most closelv related to
Asteropidae, the latter can by no means be considered as being derived directly from the former.
On the contrary, the sub-family Philomedinae must certainlv be considered to have a type
that differs verv mucli from the primitive form from which the A s t e r o p i d s originate;
the fifth limb especially must be considered as being rather much modified in this sub-familv.
On the other hand it does not seem impossible that Philomedinae and Asteropidae originate
from a common primitive form. The part of the fifth limb that was termed the first and second
exopodite joints in the homologization carried ou t by me above was presumably more power-
Zoolog bidrag, Uppsala Suppl -Bd I
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