HOW C0RAL8 GROW. 31 



posited Pig. 32, C, shows the twelve rudimentary parti- 

 i. These, after the young polyp has become stationary, 

 finally enlarge and become joined to the external wal 

 the coral now m course of formation (1 . form- 



ing a groundwork or pedestal on which the polyp n 

 l> represents 'he young polyp resting on the limestone ped- 

 I, with the tentacles well developed. 

 But little i- positively known as t<> the rate of growth of 

 corals. A common brain coral [Mceandrina labyrinthx 

 measuring a fool in diameter ami four inches thick in the 

 most convex part, attained its growth in twenty years. 



\_y 



Km 89 Development "f a coral \ 



trula; B, young polyp with 12 septa; < '. / ■ 

 with 12 tentacles; C, the corallum and limestom ning t<> Conn. 



Magnified. 



To the order of alcyonoid corals, which have but eight 

 tentacles, belong the •'sea-fan-. - ' "sea-pens," In the 



famih of sea-fans [tforgonida) the coral-stock is horny 

 or calcareous, branching tree-like, or forming a ilat not- 

 work. Qorgonia flabellum is rod or yellow, and abundant 

 on the Florida reefs. In the A:v nd the deeper, 



colder water- of the Newfoundland Hanks and St l 

 Hanks. Primnoa reseda and Paragorgia arborea grow; the 

 latter being of great Bize, the stem as thick through as one"; 

 wrist, and the whole corallum over five feet in height. 



