The
older larva (Figure 35), which resembles the mature Squilla especially
in the structure of the great raptorial feet and of the preceding pair,
still wants the six pairs of feet following the raptorial feet. The
corresponding body-segments are already well developed, an unpaired eye
is still present, the anterior antennae are already biramose, whilst the
flagellum is wanting in the posterior, and the mandibles are destitute
of palpi; the four anterior abdominal segments bear biramose natatory
feet, without branchiae; the fifth abdominal segment has no appendages,
and this is also the case with the tail, which still appears as a simple
lamina, fringed on the hinder margin with numerous short teeth. It is
evident that the larva stands essentially in the grade of Zoea.
CHAPTER 8. DEVELOPMENTAL HISTORY OF EDRIOPHTHALMA.
Less varied than that of the Stalk-eyed Crustacea is the mode of
development of the Isopoda and Amphipoda, which Leach united in the
section Edriophthalma, or Crustacea with sessile eyes.
(FIGURE 36. Embryo of Ligia in the egg, magnified 15 diam. D. yelk; L.
liver.)
The Rock-Slaters (Ligia) may serve as an example of the development of
the Isopoda. In these, as in Mysis, the caudal portion of the embryo is
bent not downwards, but upwards; as in Mysis also, a larval membrane is
first of all formed, within which the Slater is developed.
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