" "Therefore," says he, "I regard Nebalia as a
Phyllopodiform Decapod." The youngest larvae [of the Phyllopoda] are
Nauplii, which we have already met with exceptionally in some Prawns,
and which we shall now find reproduced almost without exception. The
body-segments and feet, which are sometimes so numerous, are formed
gradually from before backwards, without the indication of any
sharply-discriminated regions of the body either by the time of their
appearance or by their form. All the feet are essentially constructed in
the same manner and resemble the maxillae of the higher Crustacea.* (*
"The maxilla of the Decapod-larva (Krebslarve) is a sort of Phyllopodal
foot" (Claus).) We might regard the Phyllopoda as Zoeae which have not
arrived at the formation of a peculiarly endowed abdomen or thorax, and
instead of these have repeatedly reproduced the appendages which first
follow the Nauplius-limbs.
Of the Copepoda--some of which, living in a free state, people the fresh
waters, and in far more multifarious forms the sea, whilst others, as
parasites, infest animals of the most various classes and often become
wonderfully deformed--the developmental history, like their entire
natural history, was, until lately, in a very unsatisfactory state. It
is true, that we long ago knew that the Cyclopes of our fresh waters
were excluded in the Nauplius-form, and that we were acquainted with
some others of their young states; we had learnt, through Nordmann, that
the same earliest form belonged to several parasitic Crustacea, which
had previously passed, almost universally, as worms; but the connecting
intermediate forms which would have permitted us to refer the regions of
the body and the limbs of the larvae to those of the adult animal, were
wanting.
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