70 



ANTHOZOA. 



Fig. 31. 



(152.) The structure of the individual polyps of the Corallid resem- 

 bles that of one of the polyps of the Alcyonidae already described ; and 

 the prey obtained by each goes to the support of the general mass. 

 Their reproduction is undoubtedly from germs developed in internal 

 filamentary ovaria, which escape either through the mouth, as in 

 Alcyonium, or else, as Cavolini* supposed, through apertures placed be- 

 tween the origins of the tentacles. 



(153.) PENNATULID.E. This fa- 

 mily belongs likewise to the divi- 

 sion of cortical polyps, and agrees 

 with the two last in most points, 

 the principal distinction consisting 

 in the character of the internal 

 axis which supports the body. In 

 some species this part is reduced 

 to a ligamentous mass, inter- 

 spersed with calcareous granules ; 

 but in the most typical forms the 

 skeleton consists of several pieces, 

 capable of moving upon each other. 

 The whole animal in such cases 

 resembles a feather, the stem sup- 

 porting lateral branches, upon 

 which the polyps are arranged. 

 From the circumstance of these 

 compound animals being unat- 

 tached to any foreign support, they 

 have been supposed to be capable 

 of swimming at large in the sea, 

 by the voluntary movements of 

 their articulated branches a fact 

 strongly contested by many mo- 

 dern zoologists ; but as we can say 

 nothing from our own observation 

 upon this subject, we must leave 

 the question open to future investigation. Many species are eminently 

 phosphoric. 



(154.) TUBIPORID^E. We have now to speak of a class of polyps very 

 different in their construction from those which have been described. 

 Instead of incrusting an internal solid skeleton, the Tubiporida3 are 

 enclosed in a calcareous or coriaceous sheath or tube, from the orifice of 

 which the polyp is protruded when in search of prey : these are named 

 by authors Vaginated Polyps. 



* Cavolini (Filippo), Memorie per servire alia storia dei Polipi marini. 4to. Na- 

 ples, 1785. 



Figure of Pennatula. 



