578 THE REEF PROPER OF THE FLORIDA STRAITS. 



belong absolutely to separate classes ; and that a medusa should spring from a zoophyte is 

 hardly less surprising than that a perch should give birth to a human being. 



These important discoveries were made simultaneously by Professor Van Beneden and Sir 

 John Dalyell, and the former naturalist was able to observe a phenomenon which certainly 

 seems to be the first step towards the return from the medusa into the zoophyte. Having 

 isolated a specimen of the little medusae, and made a careful drawing of it, he left it for 

 about an hour, and on his return was surprised to find that the whole shape of the tiny being 

 had altered. The convex disc had become concave, the tentacles were reversed, and the animal 

 had changed the central footstalk of the medusa into the semblance of a zoophytic stem. 



" My observations," remarks that accomplished naturalist, as quoted by Mr. T. R. Jones, 

 "go no further; but although I have not seen the medusa give origin to a polype stem, I 

 observed it up to- the moment when it was about to form a new colony ; and without fear of 

 deceiving ourselves, we may form by analogy some idea of the changes which must necessarily 

 occur. The Campanularia, in its medusa state, has only a single aperture, situated at the 

 extremity of its central pedicle. We have already seen that its body becomes inverted like 

 the finger of a glove, and that .the marginal filaments become converted into true tentacles. 

 The polype fixes itself by the extremity of its central appendage that is, by what was previ- 

 ously its mouth ; the back of the umbrella becomes depressed at the same time that the 

 tentacles change their direction ; and in the centre of the disc a new aperture is formed, which 

 communicates with the central cavity, and becomes the permanent mouth, which is situated 

 directly opposite to the original one. 



" Being now fixed by its base, the body of the polype begins to grow ; and as its external 

 sheath becomes hardened, buds sprout at regular intervals from its surface. In a word, the 

 growth of the polype resembles that of the hydra, with this difference, that in the latter there 

 is no polype stem, and their buds sprout from another part of the body." 



The name of Campanularia is given to this zoophyte in consequence of the bell-like form 

 of its cells, and is derived from the Latin word "campana," a bell. 



The delicate PLUMULAEIA is so called on account of the feathery appearance of its polyp- 

 idon. The cells are always small and the egg-vesicles ai-e scattered. In some species the 

 stem is composed of many parallel tubes, such as Plumularia myriaphyllum, but in the 

 present species it is quite simple. The egg-vesicles are rather widely scattered. 



THE CORAL REEFS OF FLORIDA. 



THE REEF PROPER OF THE FLORIDA STRAITS does not reach the surface, excepting in 

 certain places, as follows : Carysport, where there is an iron pier lighthouse, Alligator Reef, 

 Tennessee Reef, and a few shoals of less extent, but perhaps not less dangerous. These shoals 

 give rise to heavy breakers, which show at most times in white caps. In a few places there is 

 an accumulation of dead corals and debris, which brings the surface to a level with the water ; 

 then the dry land that is formed is called a key (cayo) or islet. The Dry Tortugas are so 

 named, being originally of similar character. 



Sombrero Key is an important example, on which is a fine lighthouse. Dove Key, the 

 Sambos, and Sand Key, are others. Sand Key is situated at the entrance of the channel that 

 leads to Key West harbor, and bears one of the most important lighthouses on the coast. 

 This is about nine miles from Key West, southwesterly, and is the southernmost inhabited 

 land of the United States. 



Several safe anchorages are known, particularly at Key Largo, with from one to three 

 fathoms of water. 



The Bahamas are coral reefs and islands similar to the above. 



The westernmost portion of the Florida Reef consists of several keys that barely rise 

 above the sea, and are covered by fine white coral sand. Beach grasses have taken root, and 

 even quite large trees are flourishing. A small bush, called bay cedar, is abundant, and 

 covers some keys entirely. 



