In the Mediterranean lives the _Perella di mare_ of the Italian fishermen, the _Reclus marin_ of the Marseillaise; this Alcyonium ought, by its manner of life, to be placed near the Hydractiniæ, and has been carefully studied by Mons. Ch. Desmoulins. It is the _Alcyonium_ (_Suberites_) _domuncula_ of Lamarck and Lamouroux. The abdomen of these paguri is not only sheltered in a shell, but habitually visited by isopod crustaceans, described under the names of _Athelea_, _Prosthetes_, and _Phryxus_, which have entirely lost the livery of their order. In the same association we also find the _Liriope_, a little isopod 28 crustacean, of which much has been said, but which for a long time obstinately resisted all attempt at observation. This latter personage is an isopod crustacean, of moderate size, which chooses the Peltogaster as a place of abode, after having undergone a very curious regressive metamorphosis. In fact, the young lyriope has at first its little feet like other isopods, but in the adult state, the female loses her antennæ, and changes her buccal as well as her branchial appendages, so as to assume a different appearance. Several naturalists have already endeavoured to give the life-history of this singular Bopyrian. The illustrious Rathke of Königsberg discovered it; Professor Lilljeborg, of the University of Upsal, gave the first account of it; and finally Professor Steenstrup of Copenhagen made known its true origin. In short, the Lyriopes are Bopyrian Isopods, living on cirrhipedes (Sacculinideæ) as real messmates, if not as parasites; the male preserves his dignity and his prestige, but the female strips herself of all the attributes of her sex, and descends to the lowest degree of servitude. Faujas de Saint-Fond has mentioned a fossil hermit-crab as found in the mountain, St. Pierre de Maestricht; but he called by this name a crustacean of the genus _Callianassa_ and not a pagurus. These _Callianassæ_ are always completely isolated in the chalk, and it is probable that they have no other domicile than the sand or ooze at the bottom of the sea, in which they hollow out galleries for themselves. Lobsters act in the same manner after moulting. The _Gebiæ_ live like the Callianassæ, hidden in the mud. The _Limnaria lignorum_ and the 29 _Chelura terebrans_ dig out a retreat for themselves in wood, like the Teredines. We have just seen that the higher crustaceans, with their well-mounted eyes, their enormous antennæ, and their formidable pincers, are not all of them the great lords they pretend to be; more than one of them has to hold out its hand and to accept humbly the assistance of its neighbours.