Page:Popular Science Monthly Volume 44.djvu/86

78 belongs to the class of Ascidians, and is especially noteworthy since its embryonic history bears a strong resemblance to that of the lower vertebrates. The life history of the salpas is greatly complicated by the process of alternation of generations seen in physalia, and it was in them, in fact, that this phenomenon was first noticed.

The flight of the flying fish recalls that of some insects. When a ship plows through a school of these creatures, how they scud off on all sides like grasshoppers rising from underfoot in the fields, and by the aid of their gauze wings, the pectoral and ventral fins, fly to a place of safety! From the indistinct halo seen about these fish in flight, from the abrupt turns which they execute, going as readily against the wind as with it, and from their apparently uniform speed, we naturally infer a rapid beating of those delicate wings, as in the case of humming birds and certain insects, and this inference is probably a correct one. Many observers, however, contend that this is not a genuine flight, but scaling. According to this view, the fish project themselves with a great velocity from the water, press with their wings, held at an advantageous angle, against the air, and are thus kept up, while they are carried forward by their own inertia. Their motion would thus be gradually retarded until they finally entered the water again, like that of a stone skimmed along the surface of a pond, while on the contrary their flight appears to be quite uniform. This and other mechanical difficulties, and the fact that the beating of the fins can be clearly seen in other species of flying fish, show that the common belief that these animals fly in the strict sense of the word is probably the true one.

The vegetation of the sea is limited to the brown masses of sargassum or "gulf weed," which is most abundant in or along the borders of the Gulf Stream and may be seen growing on the sheltered reefs about Nassau. This alga is especially interesting for the wealth of marine life which it shelters. A large mass, which has been a floating island for some time, possesses in fact quite a varied fauna. If you fish up a handful of it and shake it over the deck, the little animals pour down like rain. Here are crabs and shrimps without number, some of them very delicate, no longer than a pin; barnacles, mollusks, and fish of several species, one of which, the Antennarius, regularly lives and builds its nest in these little islands. This grotesque fish is two or three inches long and nearly as broad in a vertical plane, and is variously spotted and mottled with light and dark-brown colors. Its lower fins resemble a pair of hands in shape and function, and its head recalls that of a mediæval war horse armed and plumed.

These little communities furnish a striking instance of the protective coloring of animals, a phenomenon of which there