162 



ACTINOZOA. 





Sclerenchyma imperforate. . Aporosa. 



Septa indicated by mere streaks. The- 

 ese pear-shaped, in some connected 



by a basal, creeping ccenenchyma. . Tubulosa. 

 Septa absent. Thecse crowded, cylin- 



drical, united at various heights by 

 distinct, horizontal epithecae. 

 Corallum spicular or, if thecal, corneous or 

 sub-calcareous. 



Spicules numerous, in some replaced, 

 either wholly or in part, by an imper- 

 fect, tubular corallum. 

 Spicules scanty, or replaced by particles 



of sand 



Corallum sclerobasic. 



Sclerobasis spinulous or smooth. . 

 Sclerobasis sulcate. 



Sclerobasis attached proximally. 

 Sclerobasis free. .... 



Tubiporidje. 



Alcyonidje. 



ZOANTHIDJE. 



Z. SCLEEOBASICA, 



GORGONIDJE. 

 PENNATUinm 



7. muscular System and Organs of Loco- 

 motion. — Reference has already been made to 

 the muscular system of Actinia. 



A like apparatus, presenting, however, some 

 differences of detail, appears to become differen- 

 tiated from the general periplastic substance in 

 most other Zoantharia and Alcyonaria. But the 

 power of altering the position of the body by the 

 slow alternate contractions of a normally attached 

 base is possessed only by those Zoantharia to 

 which the name of Sea-anemones is usually applied. 

 Their non-adherent allies, such as Edwardsia and 

 Cerianthus, have a highly contractile column- 

 wall, capable of greatly varying its length, and 

 of executing movements, for the most part, of a 

 feeble worm-like character. The Alcyonidw and 



ft 



its 



as 



B- 



of 



