[Illustration: Hydractinia polyclina: _a_, sterile individual; _b_, fertile individual, producing female Medusae; _d_, _e_, female Medusae, containing advanced eggs; _f_, _g_, _h_, _i_, Cluster of female Medusas, with less advanced eggs; _o_, peduncle of month, with short globular tentacles; _c_, individual with globular tentacles, upon which no Medusae have appeared, or from which they have dropped.] There is a very curious and beautiful animal, or rather community of animals, closely allied to the _Hydractinia polyclina_, which next deserves to be noticed. The Portuguese Man-of-War--so called from its bright-colored crest, which makes it so conspicuous as it sails upon the water, and the long and various streamers that hang from its lower side--is such a community of animals as I have just described, reversed in position, however, with the individuals hanging down, and the base swollen and expanded to make the air-bladder which forms its brilliant crested float. In this curious Acalephian Hydroid, or _Physalia_, the individuality of function is even more marked than in the Hydractinia. As in the latter, some of the individuals are Medusae-bearing, and others simple Hydrae; but, beside these, there are certain members of the community who act as swimmers, to carry it along through the water,--others that are its purveyors, catching the prey, by which, however, they profit only indirectly, for others are appointed to eat it, and these feeders may be seen sometimes actually gorged with the food they have devoured, and which is then distributed throughout the community by the process of digestion and circulation. [Illustration: Physalia, or Portuguese Man-of-War.]