Semper, who has studied these animals with particular care at the Philippine Islands, had the curiosity to open

the stomach of some of them, and found there, not the animals taken by the holothuriæ, but the remains of its respiratory processess which they were in the act of digesting. Is it then merely a messmate? We must have more information on this point; and if it were not accidentally that the fierasfer swallowed the walls of the compartment in which he was lodged, he ought rather to take his place among parasites. Though it lodges in the respiratory processes, as the learned professor at Wurtzburg asserts, the fierasfer may also be a messmate after the fashion of so many others which inhabit the neighbourhood of the rectum, in order the more conveniently to snap up those animals which are attracted by the odour.

The fierasfers are not the only fishes which seek assistance from the holothuriæ; a species lives at Zamboanga, to which the specific name of Scabra has been given, and in the stomach of which, says Mons. Johannes Müller, usually lives a myxinoid fish, called Enchelyophis vermicularis. Unfortunately, we are not told in what part of the stomach it resides; for all is stomach in these animals.

It is less degrading for a fish to ask assistance from one in his own rank. The Mediterranean offers a curious instance of this. Risso saw at Nice, at the commencement of this century, the monstrous fish known under the name of Beaudroie (the angler, or fishing-frog) lodging in its enormous branchial sac a fish of the family of the Murenidæ, the Apterychtus ocellatus. He is found there evidently under the condition of a messmate. Although the eels generally get their living easily, the Angler possesses fishing implements which are wanting in them, and

when both of them are immersed in the ooze, it carries on a fishery sufficiently abundant to enable it to share the spoil with others. This same angler lives in the northern seas, and there it harbours an amphipod crustacean, which until lately has escaped the vigilance of carcinologists. We shall speak of it further on.

Dr. Collingwood saw a sea anemone in the Chinese Sea, which was not less than two feet in diameter, and in the interior of which lodges a very frisky little fish, the name of which he could not tell.

Lieut. de Crispigny has observed a sea anemone (Actinia crassicornis) living on good terms with a malacopterygian fish, the Premnas biaculeatus. This fish penetrates into the interior of the anemone; the tentacles close round it, and it lives thus for a considerable time enclosed as in a living tomb. Mons. de Crispigny has kept these animals alive for more than a year, in order to make careful observations on them. A fish known by the name of Oxybeles lumbricoides has been also found in the Indian Seas, which modestly takes up his quarters in a star-fish (Asterias discoida). Another case of commensalism has been made known to us by Professor Reinhardt of Copenhagen. A siluroid of Brazil, of the genus Platystoma, a skilful fisherman, thanks to his numerous barbules, lodges in the cavity of his mouth some very small fishes, which were for a long time considered as young siluroids; it was supposed that the mother brought her progeny to maturity in the cavity of the mouth, as marsupials do in the abdominal pouch, or as some other fishes do. These messmates are perfectly developed and adult, but instead of living on the produce of their own labour, they prefer to instal themselves

in the mouth of an obliging neighbour, and to take their tithes of the succulent morsels which he swallows. This little fish has received the name of Stegophilus insidiatus. We see that in the animal world it is not always the great which take advantage of the little. Still, let us not be deceived; there are fishes in the latitude of the Island of Ceylon which really hatch their eggs in the cavity of the mouth, and we have seen some in the museum at Edinburgh, labelled with the name of Arius bookei. Louis Agassiz has made the same observation on a fish of the Amazon, which has also been recognised by Jeffreys Wyman. One fish wraps up its eggs in the fringes of its branchiæ, and protects them till they are hatched; another lays its eggs in holes hollowed out by itself in the steep banks of the river, and protects the young ones after they are hatched.