STRUCTURE OF SEA-ANEMONE 



193 



mf 



ml 



is thus divided into a number (some multiple of six) of 

 radial chambers. These are in communication at the base, 

 so that food particles from the gullet may pass into any of 

 the chambers between the partitions. Moreover, each 

 partition is perforated, not far from the mouth, by a pore, 

 besides which there is often another nearer the body wall. 

 The tentacles are continuous with the cavities between the 

 mesenteries, and thus all the parts of the body are 

 in communication. The 

 mouth is usually a longi- a 



tudinal slit, and its two 

 corners are often richly 

 ciliated. The gullet is 

 marked with longitudinal 

 grooves, two of which, 

 the *' siphonoglyphs," 

 correspond to the corners 

 of the mouth, and are 

 especially broad and deep. 

 Along these two grooves, 

 and by these two corners, 

 food particles usually pass 

 in ; but in some, one side 

 is an incurrent, the other 

 an excurrent channel. 

 Occasionally only one 

 corner of the mouth and 

 side of the gullet is thus 

 modified. The gullet often 

 extends far down into the 

 cavity of the anemone. 



It admits of a certain amount of extrusion. The mesen- 

 teries bear — {a) mesenteric filaments ; [h] retractor muscles ; 

 {c) ridges of reproductive cells, almost always either ova or 

 spermatozoa, rarely both ; and {d) in some cases oflfensive 

 threads or acontia. The mesenteric filaments seem to be 

 closely applied to the food, and perhaps secrete digest- 

 ive ferments. Intracellular digestion also occurs. Sea- 

 anemones have no sense organs ; the sapphire beads, which 

 are so well seen at the bases of the outermost tentacles of 

 the common Actinia mesembryanthemum, are batteries of 



13 



Fig. 100. — Section through sea- 

 anemone (across arrow in Figure 

 99). — After Andres. 



A, B, Directive septa; m.f., mesenteric 

 filaments ; g., genital organs ; m.L, 

 longitudinal muscles ; s., primary sep- 

 tum; s'., secondary septum; s"., tertiary 

 septum. The arrow enters between two 

 primary septa (an intraseptal cavity), 

 and passes out between two tertiary 

 septa. 



