ACTINOZOA. 



133 



mentioned, and having no connection with the 

 stomach wall, are distinguished, in accordance 

 with their relative na^^o^vness, as ^ secondary me- 

 senteries,' * tertiary mesenteries,' and so on. 



Fig. 26. 



Morphology of Actinozoa: — a, polype of Alcyonium; b, ideal 

 transverse section of the same ; c, longitudinal section of Actinia ; 

 — k', somatic cavity; ff, mesentery; 5', digestive cavity; 5, wall of 

 digestive cavity ; 0, mouth ; t, tentacles ; c/c, ectoderm ; ev, eudo- 

 derm ; fi, muscular layer ; )3', base ; p, reproductive organs ; p', 

 convoluted filaments, containing thread-cells, (a and b are en- 

 larged ; c is of the natural size.) 



The mesenteries of each cycle are arranged in 

 alternate pairs, while those belonging to opposite 

 sides of the body correspond and are similar to 

 one another. Externally, the mesenteries are 

 often indicated by lines or ridges which traverse 

 the whole length of the column, and are continued, 

 K .3 



