BRITISH ZOOPHYTES. 137 



like a bottomless sac. This cesophagus extends 

 only part way between tlie oral and pedal discs, and 

 communicates at the bottom called the " gastric ori- 

 fice," or " cardia," with the general body cavity. The 

 general body cavity is divided into compartments by 

 septa, which are lamellge or plates, springing from the 

 body wall and extending towards the oesophagus. 

 Some of these septa reach to the CBsophagus, to which 

 they are attached. These are called primary septa. 

 Between these are others reaching not quite to the 

 cesophagus ; these are called secondary septa. Between 

 these, again, are tertiary septa, and so on, each suc- 

 ceeding group of septa being smaller than the preced- 

 ing one ; so that the body of an anemone being divided 

 into six parts or systems by six primary septa, the 

 succession of septa in any one system would be shown 

 as follows — 



13 2 3 1 



the primary septa reaching to the oesophagus, and the 

 rest, according to their grade, becoming shorter and 

 shorter. 



This appearance is shown in Plate XI. fig. 3. 

 Deviations from this mode of arrangement, as in the 

 Cerianthidce, will be noticed where they occur. 



The septa, whether primary or otherwise, bend to- 

 wards the column from a point near the lower termina- 

 tion of the oesophagus, leaving the body cavity almost 

 open from below that point. 



The septa, or, as they are sometimes called, " mesen- 

 teries,^' are very important parts of structure, as they 

 bear the reproductive organs, the craspeda {cr) or me- 

 senteric filaments, and, where present, the acontia (ac). 



Such being the general appearance of the sea- 



