162 



ACTINOZOA. 



Sclerenchyma imperforate. 

 Septa indicated by mere streaks. The- 

 ose pear-shaped, in some connected 

 by a basal, creeping ccenenchyma. . 

 Septa absent. Thecse crowded, cylin- 

 drical, united at various heights by 

 distinct, horizontal epithecse. 

 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 sclerobasie. 



Sclerobasis spinulous or smooth. , 

 Sclerobasis sulcate. 



Sclerobasis attached proximally. 

 Sclerobasis free. .... 



Apoeosa. 



TuBtJXOSA. 

 TuBIPORrDy^. 



Alcyonid^. 



zoaxthid.^. 



z. scleeobasica. 



gorgonid,^. 



PeNNATI'LTD^, 



7. Husciilar System and Organs of I^oco- 



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 

 Cerianthiis, 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 Alcyonidm and 



