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certain whether it is to be considérée!, comparée! with the fifth limb in the following family, as
a primitively simple one or as having been simplifiée! secondarily; for several reasons the
latter of these two alternatives seems to me the more probable; with regard to this I shall
onlv refer to what has been written below in the second chapter of this treatise about the type
of the fifth limb in the primitive 0 stra co el s.) The exopodite, endopodite and epipodial
appendage on this limb are — i f this same method of explanation is employeel for this family
as has just been useel for the family Polycopidae — of types that differ rather slightly from
those observed in the Polycopidae. The process that is supposeel to represent the exopodite
is,however, relatively larger, the endopodite* is small relatively; the joints of the protopodite
cannot be distinguished. There is, at least in some cases, an indication of an endite proximally
of the process that has been explained as the endopodite (cf. the fifth limb of Sarsiella capsula
A. M. Norman, in G. O. Sars, 1887, pi. X. fig. 8, reproduced below, fig. IV: 2 and G. W. Müller
1894. pi. 4, fig. 28).
Cypridinidae. Family Cypridinidae (see fig. IV: 3, 4): In this family the fifth limb is both very mueh
di ffer entia t ed and (secondarily?) also of a rather marked foliaceous type. But in spite of its
complex structuré it shows a fairly great resemblance to the same limb in the families
Polycopidae and Sarsiellidae, especially to the latter. If the homologization carri ed out above is
applied to this family, we have, in my opinion, the following results: The protopodite
is powerful and offen dominâtes somewhat over the distal part of the limb; it is in most
cases divided into two joints, but sometimes, however, it is three-jointed, the proximal one
of these two joints has been divided into two more or less distinct joints; in the latter case we
can thus distinguish a procoxale, a coxale and a basale. The protopodite is armed on its
inner eclge with three endites, in most cases powerful, one on the procoxale, one on the
coxale and one on the basale. According to this method of explanation the part situated distally
of the protopodite is homologous with the exopodite; it is in most cases four- or five-jointed
(four-jointed in the accompanying figure). Of the joints of the exopodite the two proximal
ones are in most cases very strongly chitinized; each of them has on the inner edge a powerful
endite armed with brist les and teeth. The following joints differ in most cases very considerablv
from the preceding ones on account of their structure**; they are very slightly chitinized and
their bristles are in most cases rather soft and plumous. The tourth exopodite joint is, as
G. \V. MÜLLER showed as early as 1894, p. 62, sunk deeply in joint no. 3. In this way the
latter joint is divided into two lobes, one outer and one inner one; the inner lobe is, in addition,
often more or less reduced. The vibratory plate, which, according to this explanation, is to
l>e looked upon as an epipodial appendage, has almost exaetly the same type and position as the
same organ in the family Sarsiellidae. The endopodite seems to be always absent in this limb.**
Family Asteropidae: In this family the fifth limb shows, as we know, a type that differs
\ory mueh from the same appendage in other families; cf. the genus description of Asterope
* The interpretation of this part seems to me, however, rather uncertain.
’ 1 his <lillemire eaused me at first to assume that the two powerful proximal joints represented the endopodite,
ni .ivsiimplion thal seemed to be supported by fig. 4, p. 60, G. W. Müllkh. 1894 (= my fig. IV: 3). It is. however,
presumably incorrerl.
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