TYPES OF CCELENTERA — A SEA- ANEMONE. 



147 



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 longitudinal slit, 

 and its two corners are often richly ciliated. The gullet 

 is marked with longitudinal grooves, two of which, the 

 " siphonoglyphes," corres- 

 pond 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; '"£^V /*j^:. a .^m .m/- 

 but in some, one side is fp"~^li? a'^^^SsF 3 

 an incurrent, the other an l^^Sr^H & ^j^^fpm*. 

 excurrent channel. Occa- 

 sionally only one corner of 

 the mouth and side of the 

 gullet is thus modified. » 



The gullet often extends FlG . e s . -Section through sea- 

 far down into the cavity of anemone (across arrow in Figure 



the anemone. It admits 6 4 ).-After Andres. 



Of a Certain amount Of A ±, B > dire ctive septa ; m.f., mesenteric 



m. . filaments ; £-. } genital organs; ?ti.l. t 



extrUSlOn. 1 he mesenteries longitudinal muscles; s., primary 



bear-fa) mesenteric fila- ^^ pt rm. s Thet7ow?nte n ;s : b^ween 



mentS ; (b) retractor two primary septa (an intra-septal 



muscles ; (c) ridges of repro- £&* J&J""" ° ut betwee " ,w ° 

 ductive cells, almost always 



either ova or spermatozoa, rarely both ; and (d) in some cases 

 offensive threads or acontia. The mesenteric filaments seem 

 to be closely applied to the food, and perhaps secrete 

 digestive juice. 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 stinging cells. The nervous system is un- 

 centralised, and consists of superficial sensory cells con- 

 nected with a plexus of sub-epithelial ganglion cells. 



