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. In Mysis this
first larval skin may be compared to a Nauplius; in Ligia it appears
like a maggot quite destitute of appendages, but produced into a long
simple tail (Figure 37). The egg-membrane is retained longer than in
Mysis; it bursts only when the limbs of the young Slater are already
partially developed in their full number. The dorsal surface of the
Slater is united to the larval skin a little behind the head. At this
point, when the union has been dissolved a little before the change of
skin, there is a foliaceous appendage, which exists only for a short
time, and disappears before the young Slater quits the brood-pouch of
the mother.

(FIGURE 37. Maggot-like larva of Ligia, magnified 15 diam. R remains of
the egg-membrane. We see on the lower surface, from before