44 INTRODUCTION TO ZOOLOGY CHAP. 



much longer and is turned inward, so that it forms a gullet 

 extending some distance into the body-cavity (Fig. 20). 



In the Anemone also, the body -cavity is partially sub- 

 divided into radial chambers by a number of pairs of thin 

 membranous partitions or septa which grow inwards from 

 the body-wall. These partitions are some multiple of six in 

 number and are attached to the base of the oral disc above, 

 to the base of the body-wall below, and by their inner margins 

 to the wall of the gullet, so far as this extends, but from 

 the base of the gullet downwards the edges of the membranes 



FIG. 21. 



A, Transverse section of the body of an Anemone in region of gullet. 13, Trarsverse 

 section of the body in region below gullet. (Diagrammatic.) 



project freely into the body-cavity (see Fig. 20) ; hence trans- 

 verse sections taken through the body in the region of the 

 gullet will have the appearance shown in Fig. 21, A, whilst 

 those taken at a lower level will be seen as in Fig. 21, B. 



Not only do all the different chambers of the body-cavity 

 communicate with each other freely below, but each partition 

 is perforated not far from the top by one or more pores ; 

 each chamber is continued into the cavity of the tentacle 

 above it, and so all parts of the body-cavity are in free com- 

 munication. 



Muscles are present on the septa, and the arrangement of 

 these is one of the characters used in classifying Anthozoa. 

 It will be seen, by reference to Fig. 21, that the position of 

 the muscles on the two pairs of septa on either side of the 

 plane of symmetry of the body, differs from that of the 

 muscles on the other pairs of septa. 



