624 Haddon and Shackleton — A Revision of the British Actiniw. 



The coeiienchyme may occur as stolons, more or less riband-like, or as flattened 

 expansions, or, as in Palythoa, it may fill up the intervals between the polyps. 

 Some zoologists have laid stress on the systematic value of the habit of growth of 

 the coenenchyme ; but, as a matter of fact, we have often found that in the same 

 species it varies according to the surface to which the colony is attached, and 

 therefore cannot lay great stress on this character. The genus Gemmaria, as 

 defined by M°Murrich, precisely resembles Palythoa (his Corticifera), with the 

 exception of the character of the coenenchyme, it being absent or lamellar in the 

 former. We consider this a legitimate use of the character of the coenenchyme 

 for taxonomic purposes. 



The most interesting varieties of coenenchyme occur amongst those species of 

 Epizoanthus which incrust Grasteropod shells inhabited by hermit crabs. In these 

 cases the coenenchyme dissolves the lime of the shells, which it replaces by its own 

 substance; and thus the carcinsecium practically forms an isomorph of the shell. 

 The spire of the shell is the last portion to be absorbed. In describing the manner 

 in which the polyps are arranged on the coenenchyme, we employ the terms 

 "dorsal," "ventral," "anterior," "posterior," "right," and "left;" these have 

 reference solely to the position of the carcinsecium with regard to the crab when 

 walking. 



Development. — We have no account of the development of any Zoanthean, with 

 the possible exception of an observation by Van Beneden (1890), who describes 

 the anatomy of a larval Actinozoon allied to Semper's larva (Zeitschr. f. wiss Zool., 

 xvii. 1867). He regards it as a larva of a " microtypal" (brachycnemic) Zoanthean, 

 on account of the arrangement of the mesenteries. He adds: "What further 

 confirms our opinion, that our larva and that of Semper may be connected with 

 the development of the Zoanthese, is that the constitution of the mesenchymatous 

 lamella is particularly well developed, and provided with numerous cellular 

 elements, of which some have an endodermic origin, the others being derived 

 from the ectoderm" (p. 95). The senior author has very recently (Proc. Roy. 

 Dub. Soc. (N. S.), vol. vii., pt. iii., p. 127, 1891) published a small Paper on a larval 

 stage of the coral Euphyllia, which presents many of the anatomical peculiarities 

 which characterise Van Beneden's larva ; it is only fair to add that in the 

 newly-hatched larva of Euphyllia the mesogloea is thin and without cell- 

 enclosures.* 



Parasites. — Some of our specimens of Parasoanthus douglasi from Albany Pass 

 are infested by a Copepod which deposits its egg-capsule in the coelenteron or 



* Since the above was in type we have received, through the courtesy of the author, a valuable Paper 

 on "The Phylogeny of the Actinozoa," by Professor M'Murrich (1891), in which he gives an account, 

 and four figures (PL ix., figs. 5-8), of two stages in the development of a brachycnemic Zoanthean. We 

 regret we can do no more than draw attention to this Paper. 



