50 CGELENTERATA AND 



their respective genera. Those of Beroe never have 

 tentacles. Of the tentaculated genera Pleurobrachia and 

 Mnemiopsis, the former has long tentacles which never 

 diminish in size with age and is destitute of lateral lobes, 

 while the latter has widespreading lobes which increase 

 very greatly in size with advancing growth and the ten- 

 tacles become smaller and smaller in the progressive 

 growth. The adult has rudimentary tentacles. The 

 young of the Ctenophora are never sessile, with no inter- 

 mediate asexual form ; consequently the development is 

 said to be direct. 



CLASS II. ACTINOZOA. 



Coelenterates attached or free. Stomach bag-like, with 

 linear mouth opening into body cavity. Radial septa in 

 body cavity. Internal sexual bodies. Without medusi- 

 fovm gonophores, solitary or colonial. Body soft with 

 mural spicules, calcareous septa horny, flinty axis. Often 

 shrub-like, branching. . 



Actinoida. 



Tentacles twelve or numerous, hollow, sometimes per- 

 forate, rarely branched. Bodies soft. Skeleton when pres- 

 ent calcareous. Spicules absent in body. 



A. Bodies soft, generally solitary, attached or free. 



Tentacles numerous Actiniaria. 



I. Adherent. 



Disk lobed . . Actinoloba (Metridium). 

 Disk not lobed. Body covered with warts. 



Bunodes. 



Coenosarc developed. Colonial, two circles 

 of tentacles . . Polythoa (Zoanthus). 

 Tentacles, many circles. Solitary. 



Tealia (Rhodactinia, Urticina). 



