60 FLORIDA REEFS. 
single, and, though they are stony corals, they have no share in the forma- 
tion of reefs. In these, also, the tentacles miiltiply throughout life, though 
they are usually not so numerous as in the Actiniae. But a new feature is 
added to the complication of their structure, as compared with Actiniae, in 
the transverse beams which connect their vertical partitions, though they 
do not stretch across the chambers so as to form pei'fect floors, as in some 
of the higher Polyps. 
In the Astraeans, the multiplication of tentacles is more definite and lim- 
ited, rising sometimes to ninety and more, though often limited to forty-eight 
in number, and the transverse floors between the vertical partitions are more 
complete than in the Fungidae. Tlie Pontes have twelve tentacles only (PI. 
XVI., Figs. 15 and 16), never more and never less, and in them the whole 
solid frame presents a complicated system of connected beams. The Madre- 
pores have also twelve tentacles, but they have a more definite character than 
those of the Porites, on account of their regular alternation in six smaller 
and six larger ones (PI. XVIII., Figs. 5, 6, and 7) ; in these also the transverse 
floors are perfect, but exceedingly delicate. Another remarkable feature 
among the Madrepores consists in the prominence of one of the Polyps on 
the summit of the branches (PI. XIX., Fig. 7), showing a kind of subor- 
dination of the whole community to these larger individuals, and thus sus- 
taining the view expressed above, that the combination of many individuals 
into a connected community is among the Polyps a character of superiority 
when contrasted with the isolation of the ActinitiD. In the Sea-Fans, the 
Halcyonoids, as they are called in our classification, the number of tentacles 
is always eight, four of which are already present at the time of their birth, 
arranged in pairs, while the other four are added later. Their tentacles 
are loljed all around the margin, and are much more complicated in struc- 
ture than those of the preceding Polyps. 
According to the relative complication of their structure, these animals 
are classified in the followinsr order : — 
STRUCTURAL SERIES. 
Halcyonoids : eight tentacles in pairs, lobed around the margin, always couibined in large communities, 
some of which are free and movable like single animals. 
Madrepores : twelve tentacles, alternating in six larger and six smaller ones ; frequently a larger top 
animal standing prominent in the whole community, or on the summit of its branches. 
Porites: twelve tentacles, not alternating in size; system of connected beams. 
