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wie es bei den höheren Cyp riden, wo der Endopodit keine Bedeutung hat, der Fall ist.
Statt dessen muß alsdann der bei der Nahrungsaufnahme zu verwendende Teil verlängert werden,
auch ist ihre Beweglichkeit von Nutzen, um nicht von den Bewegungen des übrigen Beines abhängig
zu sein.“ It ought to be obvious that this assumption cannot be used as a proof of the accessory
nature of the forward pointing process ; as an assumption it may be taken for what it is worth.
As a proof for the exopodite nature of the vibratory plate there has also been advanced
the early appearance of this organ during ontogeny, as in other Crustacean groups the
epipodial appendages usually appear comparatively late. We should note, however, that the
forward pointing process on the fifth limb is also developed rather early; in a number of forms
it is even more powerfully developed relatively in the larvae than in the mature individuals.
It is probably impossible to draw any conclusions from these facts as to the morphologica! value
of these processes. The early appearance of these two organs during ontogeny is presumably
due less to their great phylogenetic age than to the faet that they are both of vital importance
even in the early larval stages. E. Korschelt and K. Heider state in their „Lehrbuch der
vergleichenden Entwicklungsgeschichte der wirbellosen Thiere“, p. 389, that it can by no means
be considered impossible that the early or late appearance of the epipodial appendages is closely
connected with the needs of respiration.
No really decisive evidence in favour of either of the
alternatives mentio ned can thus b e said to have been brought
forward so far, nor, in my opinion, is it possible at present to
find any. I have rnyself tried to find evidence both among the facts of comparative
mor-phology and in embryology, but without any positive result. It seems most probable to
me, however, that G. W. Müller has found the most correct solution of this problem. In
the present treatise the vibratory plates on the fifth, sixth and sevenths limbs have
conse-quently been taken to be epipodial appendages.
What was most decisive in causing me to take this view was the structure of the fifth
limb in the family Polycopidae. It is true that the assumption that the two distal, verruciform,
unjointed processes on this limb really correspond to an exopodite and an endopodite has not
yet been proved; it is only a postulate put forward by G. W. MÜLLER even with the addition
of a query, and no forms have been found so far that have enabled this statement in any way
to be changed into a proof. But it seems to me, however, as is pointed out above, fairly probable
that this assumption of G. W. MüLLER’s is correct. It seems to be supported partly by the
faet that the P o 1 y c o p i d s show primitive character istics with regard to the preceding
limbs, partly because both these processes seem to appear constantly in all the forms belonging
to this group, partly also perhaps because they are moved by special muscles in the same way.
If these two processes are homologous with the exopodite and the endopodite, the vibratory
plate must of course, as has been pointed out above, be taken as an epipodial appendage. The
shape of the vibratory plate in this group also seems to me to support the idea that it is of the
nature of an epipodial appendage.
This view is perhaps also supported by the faet that the forward pointing process on the
fifth limb is developed best in a number of forms which are at the present time looked upon
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