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The morphologica!
en lue oj the di/ferent
parts <>j the
post-orni limbs of the
(’rusturen.
But in ;i number of oases, however, the rod-shaped Unib appears to have developed directly from
the foliaceous type. As an instance of this \V. GlESBRECIIT mentions, 1913, p. 33, among other
things, „die stabbeinförmigen hinteren Maxillen und die ähnlichen Thoracopodien mancher
0 stracode n“; for these forms see below.
lt seems, however. to be bv no means impossible that the development has sometimes
proeeded in the opposite direction, that, for instance, more or less foliaceous limbs have been
developed from biramous or rod-shaped limbs. Thus,
even if we accept the assumption that the foliaceous
type is the primitive one in the Crustacea, we are not
bv any means justified in assuming a priori that we
have an original type everv time we meet this limb.
With regard to what might be called the
morphological value of the different parts of the
Crustacean post-oral limbs opinions also still differ.
Thus E. KORSCHelt and K. Heider, in their work
of 1890, are of the opinion that the exopodite and
the endopodite are organs of equal value —they refer
them, as we have seen above, to the two main branches
of the Annelidan parapodium; when in a nuinber of
forms, especially among the Malacostraca, the
endopodite forms a direct continuation of the protopodite,
while the exopodite appears in the form of a, more or
less reduced appendage, this is — according to these
authors — not to be considered as a primitive
condition; cf. loe. cit. p. 38S. On the other hand,
according to these two authors the epipodial appendages
are of a different nature from the exopodite and
endopodite; they are, as we see above, p. 22 homologized
with the dorsal cirri on the Annelidan parapodium.
J. THIELE protests against this view; in his
work of 1905, p. 466 lie writes as follows: „Dazu
bemerke ich zunächst, daß nach meiner Auffassung die
beiden Aste, Endopodit und Exopodit. ursprünglich durchaus nicht gleichwertig sind, sondern
der erstere die einfache Fortsetzung des Stammes, der letztere ein Anhang desselben, daher
kann man sie nicht wohl auf die gegabelte Gestalt der Parapodien zurückführen, sondern den
Basipoditen mit dem Endopoditen auf deren Stamm, den Exopoditen auf einen dorsalen
Anhang, etwa einen Cirrus.“
Neither of these two alternatives can be said to be proved in anv way. So far both are
to be considered as assumptions.
I n m v opinion t h e r e c o u 1 d o r i g i n a 11 y s c a r c c 1 y have been
i n y essenti a 1 mo rph o logi c a 1 d i f f ere nce ci t h er between exite s
III. - The ,,second thoracic foul" of Apus
ca net’i for/nis Sen X ff.
(From Ray I «ank ester, 1881).
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