162 ACTINOZOA. 



Sclerench}Tna imperforate. . Apobosa. 



Septa indicated by mere streaks. The- 

 cse pear-shaped, in some connected 

 by a basal, creeping coenenchyma. . Tubulosa.. 

 Septa absent, Thecse crowded, cylin- 

 drical, united at various heights by 

 distinct, horizontal epithecae. . TuBiPORiDa^ 



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. . . . Axcyonidje. 

 Spicules scanty, or replaced by particles 



of sand Zoanthid^. 



Corallum sclerobasic. 



Sclerobasis spinulous or smooth. . . Z. Sclerobasica. 

 Sclerobasis sidcate. 



Sclerobasis attached proximally. . Gorgonid^. 

 Sclerobasis free Pennatuledje. 



7. IVInseular ISysteni and Or@;ans of liOCO- 

 mction. — 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 Ediuardsia 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 Alcyonidas and 



