V.—Experiments and Observations on Crustacea: Part II. Moulting of Isopods

Abstract

(1) Ligia, like other iposods, moults in two stages. First the coverin of the abdomen with that of the posterior three thoracic segments is es uviated. About four days later the anterior covering is thrown off. Th external changes that occur in the cuticle as it ages, and the behaviou of the animal during moult, are described.(2) At the moult the cuticle splits in two main directions: (i) transvers between the fourth and fifth (free) thoracic segments; (ii) longitudina at the coxotergal junctions of (free) thoracic segments 2 to 7, there being no coxotergal split in segment 1. Coxotergal splitting is an arthrostracai if not a peracaridan, feature.(3) Ligiæ that have fasted for many weeks in sea-water may still moult normally. It follows that onset of the moult is determined by an underlying cyclic change, not as Réaumur suggested by simple growth of the animal. A second moult during the period of fast was not observed.