MacuirEe—WNotes on Certain Actiniaria. 729 
Mesoglea.—The mesogloea is not very thick; it never contains 
muscle; it is fairly homogeneous. Sections hardened in formalde- 
hyde show numerous cells. 
Endoderm.—The endoderm has the usual structure. It con- 
tains large quantities of gland-cells, both granular and homo- 
geneous, especially on the surfaces of the mesenteries. That 
lining the column and the tentacles contains numbers of alge. 
The endodermal muscle of the column is very well marked, and 
so are those of the tentacles and disc. 
Mesenteries.—The numerous gland-cells on the surfaces of the 
mesenteries have been already mentioned. The muscles have 
the usual hexactinian arrangement; the retractors do not form a 
well-marked pennon, but are distributed fairly evenly along nearly 
the whole length of the mesenteries. The parieto-basilar muscle 
is present and forms a well-marked swelling on all the mesenteries, 
except those of the fifth cycle. It is very close to the body- 
wall in sections high up, but is much further in lower down. 
The mesenterial filaments are numerous at all levels of the 
Actinia. Those in sections through the gullet show the lateral 
ridges well marked; lower down, these ridges are much lower, 
and the cells contain numerous alge. The central streak contains 
the usual gland-cells, and a few thick-walled thread-cells. 
No gonads were developed in any of my specimens, though I 
examined them both in winter and spring, and many of them 
were full of embryoes. Milne-Edwards (Hist. Nat. des Coral- 
liares, 1857, p. 240) states:—“ The production of well-developed 
young in the interior of the gastric cavity is a very well-known 
phenomenon in Actinia equina, and it appears to begin before 
the reproductive organs have arrived at maturity.” 
Since this Paper was written, I have seen an account of the 
anatomy of Actinia equina, by T. A. Simon (Beitrag zur Ana- 
tomie und Systematik der Hexactinien, Inaugural Dissertation der 
hohen philosophischen Facultét der Universitat Munchen zur 
Erlangung der Doctorwiirde, 1892, pp. 42-45). I can corroborate 
a great deal of what he says, but in some points my specimens 
seem to have differed from his. In his account of the sphincter, 
on p. 43, he says: “The strong fibrillar mesogloea is at its (the 
sphincter’s) site thickened to more than double, so that one can see 
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