THE ANATOMY OF PHORONIS AUSTRALIS. 155 
Fie. 12.—A transverse section across the tentacular crown of Ph. “ K.,” 
in order to show the shape of the lophophore in this species (cf. Fig. 7), 
the position and shape of the epistome, ep., and the glandular pit and 
ridge (g/.). 6. v. Blood-vessels. 7.¢. Inner series of tentacles. o. ¢. Outer 
series of tentacles. a. The break in the dorsal mid-line of the inner series of 
tentacles, the tentacles right and left being the youngest. 
Fig. 13.—A transverse section of a tentacle. O. Its outersurface. J. Its 
inner ciliated surface. 0. v. Tentacular blood-vessel, with contained blood- 
corpuscles. c. Tentacular portion of ccclom. ¢. Ccelomic epithelium. m. 
Muscle. xz. Nerve. s%. Mesoblastic skeleton. 
Fic. 14.—A portion of a transverse section through the base of three 
tentacles, in the region 4 of Fig. 6. 4. ¢. Basement tissue, passing from one 
surface to the other so as to form trabecule (¢7.), and separating the supra- 
septal ccelom into tentacular cavities (¢.c.). sk. Skeleton of the tentacles, 
already having a semicircular shape and forming thickenings on each side of 
the trabecule. m. Muscle-fibres. 
Fie. 15.—A longitudinal section through the oral region of the body and 
the tentacular crown, showing the somewhat conical base, around which the 
lophophore is spirally wound. The septum (S.) is seen dividing the ccclom 
into supraseptal (s. s.) and infraseptal (¢. s.) cavities. a. Anus. 0%. One of 
the lateral mesenteries in the infraseptal celom. d.v. Distributing branches 
of the afferent blood-trunk, which pass along the lophophore. g/. Glandular 
ridge. 7.g. Lophophoral groove. ¢o. Lophophoral ridge. MV. Nerve-band. 
NV'. Modification of nerve-band to form a “sense organ.” ze. Nephridial 
duct. xe. f. The large nephridial funnel, communicating with the rectal 
chamber (7. ¢.). ze. /’. Small funnel opening into the csophageal chamber 
(@.¢.). ov. Ovaincelom. *#. v. Recipient blood-vessels. §. Septum. s. s. 
Supraseptal portion of ceelom. 7. Tentacles. 
Fie. 16.—Longitudinal section of the nerve-band. 4. ¢. Basement tissue, 
continuous with the septum (S.). ep. Epidermis, which is here deeper than 
over the general surface of the body. xz. c. Nerve-cells. 
Fic. 17.—Portion of a transverse section of the lophophoral “ sense 
organ.” ep. Epidermis. .c. Nerve-cells. NN. Nerve-band. / Fibrils 
passing across it. 
Fie. 18.—A transverse section through the body along the line C D in Fig. 
23, to show the relative positions of the mesenteries, blood-vessels, and 
nephridial funnels. a. Gisophageal mesentery. af. Afferent blood-trunk. 
b. b', Right and left lateral mesenteries. 4. 7¢. Basement tissue. 4. v. Cacal 
blood-vessels. c¢. Rectal mesentery. c.c. Ceelomic corpuscles. cz. Circular 
muscles of the body wall. cz’. Circular muscles of the esophagus. ef. Effe- 
rent blood-trunk in the left lateral chamber. ep. Epidermis. f. Fibres, 
passing from the body wall to cesophagus. dg. Longitudinal muscles of the 
