The Zoaea (Fig. 123, A) differs from that of the Galatheidea mainly in the absence of the long spines. It possesses the usual appendages characteristic of the Zoaea, namely, the first and second antennae, mandibles, first and second maxillae, and two pairs of biramous swimming maxillipedes and small third maxillipedes. In the Metazoaea (B), as in the Anomura generally, the third maxillipedes develop into biramous swimming organs, a thing they never do in the Brachyura, and the rudiments of the thoracic segments put in a first appearance. The abdominal segments are already fully formed in the Zoaea stage, so that here as in all other Zoaeas, the order of development from in front backwards is disturbed by the precocious differentiation of the abdominal segments. The next stage is the “Glaucothoe” (Fig. 123, C), which corresponds to the Megalopa of Brachyura (Fig. 125, p. 183). It differs from the adult Hermit-crab in the perfect symmetry of its body, the segmented abdomen, and the presence of five pairs of normal biramous pleopods. At this stage, which lasts four or five days, it resembles closely a little Galatheid. The asymmetry of the adult (Fig. 123, D) is now imposed upon this larva by the migration of the liver, gonads, and green glands into the abdomen, and by the shifting of the posterior lobes of the liver on to the left side of the intestine, which is displaced dorsally and to the right. The gonad lies entirely on the left side. The pleopods of the right side now degenerate, more completely in the male than in the female, and this degeneration is not completed until the little crab has found a shell and lived in it for some time. If a shell is withheld from it, the degeneration of the pleopods is much retarded, so that although the Hermit-crab assumes its asymmetry without the stimulus of the spiral shell, yet this stimulus is necessary for the normal completion of the later stages. =Fam. 1. Pylochelidae.=—The abdomen is macrurous and symmetrical, with all the limbs present. _Pylocheles_ (Fig. 118, p. 173). =Fam. 2. Paguridae.=—The abdomen is asymmetrical, with some of the limbs lost. The antennal scale is well developed, and the flagella of the first antennae end in a filament. =Sub-Fam. 1. Eupagurinae.=—The third maxillipedes are wide apart at the base, and the right chelipedes are much larger than the left. _Parapagurus_ from deep-sea, _Eupagurus_ from temperate, especially north temperate seas. _Pylopagurus._ =Sub-Fam. 2. Pagurinae.=—The third maxillipedes are approximated at the base; the chelipedes are equal or subequal, or the left is much larger. Chiefly in the warm and tropical seas, but _Clibanarius_ and _Diogenes_ also in the Mediterranean.