336 



COELENTERATA ANTHOZOA 



CHAP. 



pact as the substance of a pearl. In Paragorgia and some other 

 closely related genera the spicules of the axis of the colony also 

 become tightly wedged together, but the core thus formed is far 

 more porous and brittle than it is in the Coralliidae. In 



10 



Fig. 149. Spicules of Alcyonaria. 1, Club of Juncella ; 2, waited cross of PlexaureUa ; 

 3, torch of Eunicella ; 4, needle of Renilla ; 5, warted spindle of Gorgonella ; 6, 

 spicule of Pennatula ; 7, foliate club of Eunicea ; 8, irregular spicule of Paramuricea : 

 9, scale of Primnoa ; 10, spicules of Trichogorgia. (5 and 10 original, the re- 

 mainder after Kolliker. ) 



Tubipora (the organ-pipe coral) and in Telesto rubra the spicules 

 of the body- walls of the zooids fuse to form perforated calcareous 

 tubes. In some species of Sclerophytum the large spicules of the 

 coenenchym become so closely packed that they form dense 

 stony masses, almost as hard as a Perforate Madreporarian coral. 

 The horny substance, allied chemically to keratin, plays an 



I 



