An Actinian. 21 



ing the primary chamber into smaller secondary and ter- 

 tiary chambers. 



Excretory and Respiratory System. The waste pro- 

 ducts of digestion are ejected through the opening of the 

 mouth. Certain mesenterial filaments may (?), however, 

 perform excretory and respiratory functions. These fila- 

 ments are arranged along the free edges of the mesenteries, 

 at the upper part appearing as an undulating line, while lower 

 down each filament is coiled into a tangle of considerable 

 size. Lying near the base of the mesenteries, in the deeper 

 part of the coelenteric chamber, are greatly elongated mes- 

 enterial filaments; the coiled acontia. 



The Reproductive Organs lie near the free edges of the 

 mesenteries on each side of the mesenterial filaments. Each 

 gland is a somewhat convoluted structure that dehisces its 

 contents, eggs or spermatozoa, into the coelenteric cavity. 

 Are mesenterial filaments, acontia and sexual organs present 

 on the primary septa? 



The Muscular System. Though muscle fibres are pres- 

 ent in the walls of the column, around the disc and around 

 the mouth, the most characteristic muscles are developed 

 along the septa, where they run vertically as longitudinal 

 retractors. Are they on the inter- or intra-septal wall ? Does 

 the arrangement on the primary mesenteries differ from the 

 arrangement elsewhere? 1 



The Digestive and Circulatory System. - The sea- 

 water freely mixes with the products of digestion, and the 



1 The tentacular retractors are arranged on the inter-septal walls of 

 the directive septa; on the other septa they are on the intra-septal 

 walls. 



