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 medusze, 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 dise 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, 
“oo 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 PLUMULARIA is so called on account of the feathery appearance of its polyp- 
idon. The cells are always small and the egg-vesicles are scattered. In some species the 
stem is composed of many parallel tubes, such as Plumularia myriophyllum, but in the 
present species it is quite simple. The egg-vesicles are rather widely scattered. 
ADISEID, (CKONERIANIE, IRU2 IIIS Ola | MILO JRUILID ANG 
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 débris, 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. 
