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 multiply 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 Actinias, in 

 the transverse beams which connect their vertical partitions, though they 

 do not stretch across the chambers so as to form perfect floors, as in some 

 of the higher Polyps. 



In the AstroBans, 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. The Porites 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. XVIIL, 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 Polj^ps 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 wdth the isolation of the Actiniae. In the Sea-Fans, the 

 Halc^'onoids, 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 lobed 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 following order : — 



STRUCTURAL SERIES. 



Halcyonoids : eight tentacles in pairs, lobed around the margin, always coiabined in large communities, 



some of which are free and movable lii<e single animals. 

 Madrepores : twelve tentacles, alternating in six larger and six smaller ones ; fretiuently 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. 



