y8 THE POPULAR SCIENCE MONTHLY. 



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 ven- 

 tral fins, fly to a place of safety ! From the indistinct halo seen 

 about these fish in flight, from the abrupt turns which they exe- 

 cute, 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 ob- 

 servers, 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 uni- 

 form. 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 interest- 

 ing 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 vari- 

 ously 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 mediaeval war horse armed and plumed. 



These little communities furnish a striking instance of the 

 protective coloring of animals, a phenomenon of which there 



