SUBDIVISIONS OF ACTINOID POLYPS. 61 



The tribes adopted are those recognized by Prof. Verrill, 

 and have the limits he has assigned to them. The classification 

 diverges from his system in uniting the non-coral-making 

 and coral-making species into one grand division, that of the 

 Actinoids (on the ground of the close resemblance of the 

 polyps), and also in separating from the latter the Cyatho- 

 phylloid corals, for the reasons mentioned on page 21. Some 

 of the figures of corals on former pages are here repeated in 

 order to present together those of like relations. 



1. Species without internal Coral Secretions. Actesakia of 



Verrill. 



1. The Actinia tribe, or Actdnacea, secrete no coral inter- 

 nally, and moreover have a muscular base, with some degree 

 of locomotion by means of it. The Actiniae of the frontis- 

 piece, and of pages 23, 26, are examples. 



2. The Zoanthus tribe, or Zoanthacea. The species here 

 included are like the Actiniae in secreting no coral. But while 

 they have a base, it is not muscular, and they are never capable 

 of locomotion. The polyps have a thick or somewhat leath- 

 ery exterior, and, as already observed (p. 39), have gills, or 

 branchiae. Some of the species are solitary polyps ; but 

 generally they form compound masses or zoothomes, 

 by budding; sometimes making simple lines of polyps 

 over a supporting surface; at other times incrusting plates, 

 or irregular masses. The following figure (from Verrill) 

 represents a species found in American seas off the coast of 

 New Jersey, in deep water, and also in Massachusetts Bay, 

 which has a habit of fixing on a shell for its support and of 

 always taking one containing a soldier crab. The shell 

 finally becomes dissolved away — how, it is not known, by 



