THELACEROS RHIZOPHORA. 563 
EXPLANATION OF PLATE XXXVI, 
Illustrating Mr. P. Chalmers Mitchell’s paper on “ Thela- 
ceros rhizophore, n. g. et sp., an Actinian from Celebes.” 
Fic. 1.—Diagram of the tentacles and mesenteries in Thelaceros rhizo- 
phore. The tentacles are represented by unshaded circles; the endoccles 
of the four orders are variously shaded; the exocceles are unshaded. D. 
Directive mesenteries. 1 and 2. Pairs of mesenteries of the first and second 
order. 3. Pair of mesenteries of the third order. 4. Pair of mesenteries of 
the fourth order. ¢. Exoccelic tentacle. 7, ¢,, ¢,, ¢,. Tentacles of the corre- 
sponding endoceeles. 
Fic. 2.—Tentacle. x 4°5. 
Fie. 3.—Under surface of a tentacle with the cavity opened, showing the 
entrance into the cavities of the protuberances. 
Fic. 4.—Transverse section through a part of a tentacle and protuberance. 
a. Cavity of tentacle. 4. Cavity of tentacular outgrowth. ez. Endoderm ; 
the cell outlines have all disappeared, and only a thick layer of parasitic alge 
are left. mg. Mesoglcea, with fine fibrils. mm. 2. Ectodermal muscular layer, 
forming in the tentacle a folded layer of fibres in transverse section, with 
occasionally a part occluded in the mesoglea. m. 7. 1. Ectodermal muscular 
layer of protuberance ; fibres cut obliquely. x. 7. Nervous layer. e./. Ecto- 
dermal epithelium with nettle-cells, young nettle-cells, and nuclei. 
Fie. 5.—Part of the oral disc. 7.1, ¢. 2. Tentacles of the inner circle 
belonging to the first and second orders. 7. 4, ¢. 3, ¢. 4, form one of the sets 
of three. ¢, ¢, ¢, ¢. Tentacles of the outer circle. The mesenteries are seen 
as lines, extending from each side of the base of each tentacle towards the 
stomodeum. On the oral disc, between the mesenteric lines, are seen the 
accessory tentacles. 
Fie. 6.—Inner (endoccelic) face of a mesentery of the first order, with the 
adjacent exoceelic tentacle. 4. w. Body wall, thick in the column and on the 
base, thin on the disc. 7. m.1, /. m. 3, 1. m.4. Longitudinal muscle. J/. m. 2. 
Parieto-basilar muscle. s¢. Stomodeum. g. Genital organ. m.f Contorted 
edge of mesentery, with filament. 
