der niederen Thiere während des Jahres 1859. 165 



Class I. Hydrozott' 



Coelenterate animals , in which the wall of the digestive sac 

 is identical with that of the general cavity of the body, and the re- 

 productive Organs are external. 



Order 1. Hydridae. Animal consisling of a Single naked po- 

 lype. Locomotive. 



Order 2. Tiibularidae. Animal consisting of one polype or of 

 several connected by a coenosark. Fixed. Polypes naked. 



Order 3. Sertularidae. Animal consisting of several polyps 

 connected by a coenosark. Fixed. Polypes protected by cells. 



Order 4. Calycophoridae. Animal consisting of several poly- 

 pes connected by a coenosark, furnished with natatorial organs. 

 Oceanic. 



Order 5. Physophoridae. Animal consisting of several poly- 

 pes connected by a coenosark , with or without natatorial organs. 

 Upper extremity of coenosark dilated into a float. Oceanic. 



Order 6. Medusidae. Animal consisting of a polype suspen- 

 ded from the under surface of a natatorial organ. Oceanic. 



Order 7. Lucernaridae. Animal consisting of a polype situa- 

 ted in the centre of a natatorial organ furnished with adherent base. 

 Oceanic. 



Class II. Actino zoa. 



Coelenterate animals, in with the wall of the digestive sac is 

 separated from that of the general cavity of the body by a interve- 

 ning Space, subdivided into Chambers by a series of vertical periga- 

 stric partitions, on the sides of which the productive bodies are 

 situated. 



a. Parts of the body in number some multiple of five or six. 

 Order 1. Zoantharia. Polypes with simple (rarely branched) 



tentacula, usually numerous. Solitary or aggregated. Sedentary or 

 locomotive, seldom oceanic. 



b. Parts of the body in number some multiple of four. 

 Order 2. Rugosa. Animal unknown. Corallum thecal , with 



septa and tabulae. 



Order 3. Älcyonaria. Polypes with eight fringed tentacula. 

 Always aggregated. Kever locomotive. 



Order 4. Ctenophora. Oceanic, free swimming , transparent, 

 gelatinous Actinozoa , moowing by mcans of vertical rows of cili- 

 ated plates. 



Auch van Beneden vereinigt -die echten Polypen 

 mit den Cuvier'schen Akalephen zu einer gemeinschaft- 

 lichen Abtheilung, für die er (mit Umgehung des von Ref. 



