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FAMILY II.— ZOANTHIDiE. 



The polypes in this family are persistently fixed, and 

 aggregated : the adherent base extending itself laterally, 

 and sending up new polypes at intervals, which remain 

 permanently united to each other, and to the primary 

 polype. The extension may be in irregular lines, carrying 

 the polypes in single file; in broad bands, supporting several 

 abreast ; or in all directions, producing large clustered 

 masses, incrusting the foreign body to which they happen 

 to be adherent. 



This variation in the manner of base-extension has been 

 hitherto considered as so important, that genera have been 

 constituted on this character alone, — Zoanthus, including 

 those whose base runs in lines ; Palythoa, such as form 

 carpet- like surfaces. But evidence will presently be 

 adduced to show that these variations may occur in the 

 same species. Again, the genera MammiUfera and Corti- 

 cifera, of Lesueur, have been formed for clustered species ; 

 the former being fleshy, with a mucous surface, not en- 

 veloped in sand ; the latter " inclosed in cellules of sand, 

 agglutinated ; the cellules themselves agglutinated for their 

 whole length, and forming a corticiferous expansion." It 

 appears, however, from Lesueur's own description, that 

 what he considered " cellules," inhabited by the animals, 

 was simply the integument of each polype, in which sand 

 was imbedded. The presence or absence of sand, however, 

 can in no wise be allowed to constitute a generic distinc- 

 tion. I cannot, therefore, recognise in the family more 

 than the single genus, Zoanthus. 



