ACTINOZOA. 



157 



costse, thus representing the dissepiments ; and a 

 continuous layer, or * epitheca ', consisting of the 

 coalesced, external, indications of tabula?. 



It needs scarcely to be stated that an organism 

 producing such a structure as the foregoing must 

 closely have resembled, in every essential respect, 

 the Actinia, or typical polype, previously de- 

 scribed. The relations of the septa and pali to the 

 mesenteries, of the theca to the column wall, of 

 the columella to that part of the enderon which 

 forms the floor of the somatic cavity below the 

 digestive sac, are, indeed, sufficiently obvious. 

 The septa, too, like the mesenteries, are primary, 

 secondary, and tertiary, according to their degree 

 of approximation to the columella; the primary 

 septa alone being in direct contact therewith. All 

 these parts are, in the living animal, completely 

 concealed by the soft integuments : the digestive 

 sac, and much of the somatic cavity, especially its 

 upper portion, performing, as in the soft-bodied 

 species, their proper nutrient and reproductive 

 functions (Jig. 33). 



In a similar manner is the ccenenchyma de- 



(fi9- 



It may be 



united with the corallites at their bases only, thus 

 forming a creeping expansion or stalk, or become 

 connected with them throughout the greater por- 

 tion of their height. There are even cases in 

 which the corallites appear sunk amid a very 

 abundant coenenchyma, while, in others, the same 

 structure is but sparingly developed. The relative 

 distance of the corallites from one another is also 

 subject to much variation. 



But the typical structure of the corallite above 

 described does not admit of being studied in any 



