120 MANUAL OF ZOOLOGY SECT. 



zooids), ordinary zooids, and siphonozooids, which are smaller, 

 and are devoid of tentacles and of gonads. 



None of the Sea-anemones have a true skeleton ; in some, 

 however, there is a thick cuticle, and several kinds enclose 

 themselves in a more or less complete tube, which may be 

 largely formed of discharged nematocysts. In some 

 Alcyonaria, such as the " Dead mens' fingers " (Alcyonium, 



FIG. 56. Tubipora musica. Skeleton of entire colony. //. platform. 

 (After Cuvier.) 



Fig- 55) tne skeleton consists of minute, scattered, irregular 

 deposits of carbonate of lime called spicuks. In Tubipora 

 (the " organ-pipe coral ") (Fig. 56) there is a continuous 

 calcareous tube for each polype. In the Red Coral of 

 commerce (Fig. 54) there is an extremely hard calcareous 

 branched rod which extends as an axis through the ccenosarc. 

 In the Black Corals (Antipathes and allies) there is a horn- 



