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the preceding literature. For several reasons the terms: fifth, sixth and seventh limbs
seems to me most convenient; i. e. in the case of these organs onc of the two methods
recommended by G. W. Müller in his work of 1894 (cf. the quotation on p. 19 above)
has been adopted.
Pre-oral limbs*: —
First antenna: — With regard to this appendage I follow the terminologv
used by G. W. Müller in all essential points. On this appendage, as on all the following
ones, the joints are reckoned proximo-distally, u n 1 e s s something is s a i d to the
contra ry. In naming the different sides of the joints on this appendage, as on the
following ones, the appendage is always thought of in its natural position of rest, unless
something is said to the contrary. It is to be noted that the sides on which the joints border
on each other are always called the proximal and the distal sides; if attention is paid to
this, there is no danger of any mistakes.
Post-oral limbs: —
The post-oral limbs of the Crustacea may, as is known, be divided into three main
types according to their structure: the leaf-like or foliaceous, the biramous and the
rod-shaped limbs.
The first type is found in the Phyllopods and is characterized by W. GlESBRECHT
in his work of 1913, p. 31 as follows: The leaf-like limb consists of a lamella with an anterior
and a posterior surface and with medial, distal and lateral edges: the edges are provided with
hairs and bristles and have lobes and processes. Its middle piece is called the protopodite,
the lobes and processes are called exites, if they are situated on the latéral edge of the lamella,
endites, if they issue from its medial edge. In a number of forms the protopodite appears to
be — though sometimes only rather incompletely — divided into transverse joints. The exites
and endites may sometimes not only be bounded from the protopodite but also divided more
or less distinctly into joints themselves.
The second type of limbs is described by W. GlESBRECHT in liis work just quoted as
follows: The biramous limb consists of a trunk, the protopodite and two branches, an outer
one called the exopodite and an inner one called the endopodite. Proximally of the exopodite
and the endopodite exites and endites may occur on the protopodite; the former are called
epipodites. The protopodite of the biramous limb is proportionately less strongly developed
than in the foliaceous limb and is in most cases divided into two joints, the proximal one of
which is called the coxale, the distal one the basale. It is to be noted that in most cases probablv
only the distal part of the protopodite of the leaf-like limb, the part that has the exites, is to
be considered as homologous to the protopodite of the biramous limb; that part of the
protopodite of the latter type which corresponds to the proximal part of the protopodite of the
former type seems, in most cases, to have been more or less completely united to the body of
the animal. Sometimes, when this union is less complete, one can, however, observe a joint
or the remains of a joint between the coxale and the body; this joint is usually called the pro-
* Ci. W. Müller in his work oï 1894 considered bol h the firsl and second antennae as j»re-oral. Now, as is well
known, the second antennae of ail Crustacea have been shown to be post-oral.
First antenna.
Post-oral limbs.
A general description
of the main types of
the post-oral limbs of
the Crustacea.
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